List of finite simple groups

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In mathematics, the classification of finite simple groups states that every finite simple group is cyclic, or alternating, or in one of 16 families of groups of Lie type (including the Tits group, which strictly speaking is not of Lie type), or one of 26 sporadic groups.

The list below gives all finite simple groups, together with their order, the size of the Schur multiplier, the size of the outer automorphism group, usually some small representations, and lists of all duplicates. (In removing duplicates it is useful to note that finite simple groups are determined by their orders, except that the group Bn(q) has the same order as Cn(q) for q odd, n > 2; and the groups A8 = A3(2) and A2(4) both have orders 20160.)

Notation: n is a positive integer, q > 1 is a power of a prime number p, and is the order of some underlying finite field. The order of the outer automorphism group is written as d·f·g, where d is the order of the group of "diagonal automorphisms", f is the order of the (cyclic) group of "field automorphisms" (generated by a Frobenius automorphism), and g is the order of the group of "graph automorphisms" (coming from automorphisms of the Dynkin diagram).

Contents

[edit] Infinite families

[edit] Cyclic groups Zp

Simplicity: Always simple.

Order: p

Schur multiplier: Trivial.

Outer automorphism group: Cyclic of order p-1.

Other names: Z/pZ

Remarks: These are the only simple groups that are not perfect.

[edit] An, n > 4, Alternating groups

Simplicity: Solvable for n < 5, otherwise simple.

Order: n!/2 when n > 1.

Schur multiplier: 2 for n = 5 or n > 7, 6 for n = 6 or 7.

Outer automorphism group: In general 2. Exceptions: for n = 1, n = 2, it is trivial, and for n = 6, it has order 4 (elementary abelian).

Other names: Altn.

There is an unfortunate conflict with the notation for the (unrelated) groups An(q), and some authors use various different fonts for An to distinguish them. In particular, in this article we make the distinction by setting the alternating groups An in Roman font and the Lie-type groups An(q) in italic.

Isomorphisms: A1 and A2 are trivial. A3 is cyclic of order 3. A4 is isomorphic to A1(3) (solvable). A5 is isomorphic to A1(4) and to A1(5). A6 is isomorphic to A1(9) and to the derived group B2(2)'. A8 is isomorphic to A3(2).

Remarks: An index 2 subgroup of the symmetric group of permutations of n points when n > 1.

[edit] An(q) Chevalley groups, linear groups

Simplicity: A1(2) and A1(3) are solvable, the others are simple.

Order:


{1\over (n+1,q-1)}
q^{n(n+1)/2}
\prod_{i=1}^n(q^{i+1}-1)

Schur multiplier: For the simple groups it is cyclic of order (n+1, q − 1) except for A1(4) (order 2), A1(9) (order 6), A2(2) (order 2), A2(4) (order 48, product of cyclic groups of orders 3, 4, 4), A3(2) (order 2).

Outer automorphism group: (2, q − 1) ·f·1 for n = 1; (n+1, q − 1) ·f·2 for n > 1, where q = pf.

Other names: Projective special linear groups, PSLn+1(q), Ln+1(q), PSL(n+1,q)

Isomorphisms: A1(2) is isomorphic to the symmetric group on 3 points of order 6. A1(3) is isomorphic to the alternating group A4 (solvable). A1(4) and A1(5) are isomorphic, and are both isomorphic to the alternating group A5. A1(7) and A2(2) are isomorphic. A1(8) is isomorphic to the derived group 2G2(3)′. A1(9) is isomorphic to A6 and to the derived group B2(2)′. A3(2) is isomorphic to A8.

Remarks: These groups are obtained from the general linear groups GLn+1(q) by taking the elements of determinant 1 (giving the special linear groups SLn+1(q)) and then quotienting out by the center.

[edit] Bn(q) n > 1 Chevalley groups, orthogonal group

Simplicity: B2(2) is not simple and has a simple subgroup of index 2; the others are simple.

Order:


{1\over (2,q-1)}
q^{n^2}
\prod_{i=1}^n(q^{2i}-1)

Schur multiplier: (2,q − 1) except for B2(2) = S6 (order 2 for B2(2), order 6 for B2(2)′) and B3(2) (order 2) and B3(3) (order 6).

Outer automorphism group: (2, q − 1) ·f·1 for q odd or n>2; (2, q − 1) ·f·2 if q is even and n=2, where q = pf.

Other names: O2n+1(q), Ω2n+1(q) (for q odd).

Isomorphisms: Bn(2m) is isomorphic to Cn(2m). B2(2) is isomorphic to the symmetric group on 6 points, and the derived group B2(2)′ is isomorphic to A1(9) and to A6. B2(3) is isomorphic to 2A3(22).

Remarks: This is the group obtained from the orthogonal group in dimension 2n+1 by taking the kernel of the determinant and spinor norm maps. B1(q) also exists, but is the same as A1(q). B2(q) has a non-trivial graph automorphism when q is a power of 2.

[edit] Cn(q) n > 2 Chevalley groups, symplectic groups

Simplicity: All simple.

Order:


{1\over (2,q-1)}
q^{n^2}
\prod_{i=1}^n(q^{2i}-1)

Schur multiplier: (2,q − 1) except for C3(2) (order 2).

Outer automorphism group: (2, q − 1) ·f·1 where q = pf.

Other names: Projective symplectic group, PSp2n(q), PSpn(q) (not recommended), S2n(q).

Isomorphisms: Cn(2m) is isomorphic to Bn(2m)

Remarks: This group is obtained from the symplectic group in 2n dimensions by quotienting out the center. C1(q) also exists, but is the same as A1(q). C2(q) also exists, but is the same as B2(q).

[edit] Dn(q) n > 3 Chevalley groups, orthogonal groups

Simplicity: All simple.

Order:


{1\over (4,q^n-1)}
q^{n(n-1)}
(q^n-1)
\prod_{i=1}^{n-1}(q^{2i}-1)

Schur multiplier: The order is (4, qn-1) (cyclic for n odd, elementary abelian for n even) except for D4(2) (order 4, elementary abelian).

Outer automorphism group: (2, q − 1) 2·f·S3 for n=4, (2, q − 1) 2·f·2 for n>4 even, (4, qn − 1) 2·f·2 for n odd, where q = pf, and S3 is the symmetric group on 3 points of order 6.

Other names: O2n+(q), 2n+(q).

Remarks: This is the group obtained from the split orthogonal group in dimension 2n by taking the kernel of the determinant (or Dickson invariant in characteristic 2) and spinor norm maps and then killing the center. The groups of type D4 have an unusually large diagram automorphism group of order 6, containing the triality automorphism. D2(q) also exists, but is the same as A1(qA1(q). D3(q) also exists, but is the same as A3(q).

[edit] E6(q) Chevalley groups

Simplicity: All simple.

Order: q36 (q12−1) (q9−1) (q8−1) (q6−1) (q5−1) (q2−1) /(3,q-1)

Schur multiplier: (3,q − 1)

Outer automorphism group: (3, q − 1) ·f·2 where q = pf.

Other names: Exceptional Chevalley group.

Remarks: Has two representations of dimension 27, and acts on the Lie algebra of dimension 78.

[edit] E7(q) Chevalley groups

Simplicity: All simple.

Order: q63 (q18−1) (q14−1) (q12−1) (q10−1) (q8−1) (q6−1) (q2−1) /(2,q-1)

Schur multiplier: (2,q − 1)

Outer automorphism group: (2, q − 1) ·f·1 where q = pf.

Other names: Exceptional Chevalley group.

Remarks: Has a representations of dimension 56, and acts on the corresponding Lie algebra of dimension 133.

[edit] E8(q) Chevalley groups

Simplicity: All simple.

Order: q120 (q30−1) (q24−1) (q20−1) (q18−1) (q14−1) (q12−1) (q8−1) (q2−1)

Schur multiplier: Trivial.

Outer automorphism group:f·1 where q = pf.

Other names: Exceptional Chevalley group.

Remarks: It acts on the corresponding Lie algebra of dimension 248. E8(3) contains the Thompson simple group.

[edit] F4(q) Chevalley groups

Simplicity: All simple.

Order: q24 (q12−1) (q8−1) (q6−1) (q2−1)

Schur multiplier: Trivial except for F4(2) (order 2).

Outer automorphism group:f·1 for q odd, 1·f·2 for q even, where q = pf.

Other names: Exceptional Chevalley group.

Remarks: These groups act on 27 dimensional exceptional Jordan algebras, which gives them 26 dimensional representations. They also act on the corresponding Lie algebras of dimension 52. F4(q) has a non-trivial graph automorphism when q is a power of 2.

[edit] G2(q) Chevalley groups

Simplicity: G2(2) is not simple but has a simple subgroup of index 2; the others are simple.

Order: q6 (q6−1) (q2−1)

Schur multiplier: Trivial for the simple groups except for G2(3) (order 3) and G2(4) (order 2).

Outer automorphism group:f·1 for q not a power of 3, 1·f·2 for q a power of 3, where q = pf.

Other names: Exceptional Chevalley group.

Isomorphisms: The derived group G2(2)′ is isomorphic to 2A2(32).

Remarks: These groups are the automorphism groups of 8-dimensional Cayley algebras over finite fields, which gives them 7 dimensional representations. They also act on the corresponding Lie algebras of dimension 14. G2(q) has a non-trivial graph automorphism when q is a power of 3.

[edit] 2An(q2) n > 1 Steinberg groups, unitary groups

Simplicity: 2A2(22) is solvable, the others are simple.

Order:


{1\over (n+1,q+1)}
q^{n(n+1)/2}
\prod_{i=1}^n(q^{i+1}-(-1)^{i+1})

Schur multiplier: Cyclic of order (n + 1, q + 1) for the simple groups, except for 2A3(22) (order 2), 2A3(32) (order 36, product of cyclic groups of orders 3,3,4), 2A5(22) (order 12, product of cyclic groups of orders 2,2,3)

Outer automorphism group: (n+1, q + 1) ·f·1 where q2 = pf.

Other names: Twisted chevalley group, projective special unitary group, PSUn+1(q), PSU(n+1, q), Un+1(q), 2An(q), 2An(q, q2)

Isomorphisms: The solvable group 2A2(22) is isomorphic to an extension of the order 8 quaternion group by an elementary abelian group of order 9. 2A2(32) is isomorphic to the derived group G2(2)′. 2A3(22) is isomorphic to B2(3).

Remarks: This is obtained from the unitary group in n+1 dimensions by taking the subgroup of elements of determinant 1 and then quotienting out by the center.

[edit] 2Dn(q2) n > 3 Steinberg groups, orthogonal groups

Simplicity: All simple.

Order:


{1\over (4,q^n+1)}
q^{n(n-1)}
(q^n+1)
\prod_{i=1}^{n-1}(q^{2i}-1)

Schur multiplier: Cyclic of order (4, qn + 1).

Outer automorphism group: (4, qn + 1) ·f·1 where q2 = pf.

Other names: 2Dn(q), O2n(q), 2n(q), twisted chevalley group.

Remarks: This is the group obtained from the non-split orthogonal group in dimension 2n by taking the kernel of the determinant (or Dickson invariant in characteristic 2) and spinor norm maps and then killing the center. 2D2(q2) also exists, but is the same as A1(q). 2D3(q2) also exists, but is the same as 2A3(q2).

[edit] 2E6(q2) Steinberg groups

Simplicity: All simple.

Order: q36 (q12−1) (q9+1) (q8−1) (q6−1) (q5+1) (q2−1) /(3,q+1)

Schur multiplier: (3, q + 1) except for 2E6(22) (order 12, product of cyclic groups of orders 2,2,3).

Outer automorphism group: (3, q + 1) ·f·1 where q2 = pf.

Other names: 2E6(q), twisted Chevalley group.

Remarks: One of the exceptional double covers of 2E6(22) is a subgroup of the baby monster group, and the exceptional central extension by the elementary abelian group of order 4 is a subgroup of the monster group.

[edit] 3D4(q3) Steinberg groups

Simplicity: All simple.

Order: q12 (q8+q4+1) (q6−1) (q2−1)

Schur multiplier: Trivial.

Outer automorphism group:f·1 where q3 = pf.

Other names: 3D4(q), Twisted Chevalley groups.

Remarks: 3D4(23) acts on the unique even 26 dimensional lattice of determinant 3 with no roots.

[edit] 2B2(22n+1) Suzuki groups

Simplicity: Simple for n>1. The group 2B2(2) is solvable.

Order: q2 (q2+1) (q−1) where q = 22n+1.

Schur multiplier: Trivial for n>2, elementary abelian of order 4 for 2B2(8).

Outer automorphism group:f·1 where f = 2n+1.

Other names: Suz(22n+1), Sz(22n+1).

Isomorphisms: 2B2(2) is the Frobenius group of order 20.

Remarks: Suzuki group are Zassenhaus groups acting on sets of size (22n+1)2+1, and have 4 dimensional representations over the field with 22n+1 elements. They are the only non-cyclic simple groups whose order is not divisible by 3. They are not related to the sporadic Suzuki group.

[edit] 2F4(22n+1) Ree groups, Tits group

Simplicity: Simple for n>1. The derived group 2F4(2)′ is simple of index 2 in 2F4(2), and is called the Tits group, named for the Belgian mathematician Jacques Tits.

Order: q12 (q6+1) (q4−1) (q3+1) (q−1) where q = 22n+1.

The Tits group has order 17971200 = 211 · 33 · 52 · 13.

Schur multiplier: Trivial for n>1 and for the Tits group.

Outer automorphism group:f·1 where f = 2n+1. Order 2 for the Tits group.

Remarks: The Tits group is strictly speaking not a group of Lie type, and in particular it is not the group of points of a connected simple algebraic group with values in some field, nor does it have a BN pair. However most authors count it as a sort of honorary group of Lie type.

[edit] 2G2(32n+1) Ree groups

Simplicity: Simple for n>1. The group 2G2(3) is not simple, but its derived group 2G2(3)′ is a simple subgroup of index 3.

Order: q3 (q3+1) (q−1) where q = 32n+1

Schur multiplier: Trivial for n>1 and for 2G2(3)′.

Outer automorphism group:f·1 where f = 2n+1.

Other names: Ree(32n+1), R(32n+1).

Isomorphisms: The derived group 2G2(3)′ is isomorphic to A1(8).

Remarks: 2G2(32n+1) has a doubly transitive permutation representation on 33(2n+1)+1 points and acts on a 7 dimensional vector space over the field with 32n+1 elements.

[edit] Sporadic groups

[edit] Mathieu group M11

Order: 24 · 32 · 5 · 11=7920

Schur multiplier: Trivial.

Outer automorphism group: Trivial.

Remarks: A 4-transitive permutation group on 11 points, and the point stabilizer in M12. The subgroup fixing a point is sometimes called M10, and has a subgroup of index 2 isomorphic to the alternating group A6.

[edit] Mathieu group M12

Order: 26 · 33 · 5 · 11=95040

Schur multiplier: Order 2.

Outer automorphism group: Order 2.

Remarks: A 5-transitive permutation group on 12 points.

[edit] Mathieu group M22

Order: 27 · 32 · 5 · 7 · 11 = 443520

Schur multiplier: Cyclic of order 12. There were several mistakes made in the initial calculations of the Schur multiplier, so some older books and papers list incorrect values. (This caused an error in the title of Janko's original 1976 paper "A new finite simple group of order 86,775,571,046,077,562,880 which possesses M24 and the full covering group of M22 as subgroups. J. Algebra 42 (1976), 564–596." giving evidence for the existence of the group J4. At the time it was thought that the full covering group of M22 was 6·M22. In fact J4 has no subgroup 12·M22.)

Outer automorphism group: Order 2.

Remarks: A 3-transitive permutation group on 22 points.

[edit] Mathieu group M23

Order: 27 · 32 · 5 · 7 · 11 · 23=10200960

Schur multiplier: Trivial.

Outer automorphism group: Trivial.

Remarks: A 4-transitive permutation group on 23 points, contained in M24.

[edit] Mathieu group M24

Order: 210 · 33 · 5 · 7 · 11 · 23= 244823040

Schur multiplier: Trivial.

Outer automorphism group: Trivial.

Remarks: A 5-transitive permutation group on 24 points.

[edit] Janko group J1

Order: 23 · 3 · 5 · 7 · 11 · 19 = 175560

Schur multiplier: Trivial.

Outer automorphism group: Trivial.

Other names: J(1), J(11)

Remarks: It is a subgroup of G2(11), and so has a 7 dimensional representation over the field with 11 elements.

[edit] Janko group J2

Order: 27 · 33 · 52 · 7 = 604800

Schur multiplier: Order 2.

Outer automorphism group: Order 2.

Other names: Hall-Janko group, HJ

Remarks: It is the automorphism group of a rank 3 graph on 100 points, and is also contained in G2(4).

[edit] Janko group J3

Order: 27 · 35 · 5 · 17 · 19 = 50232960

Schur multiplier: Order 3.

Outer automorphism group: Order 2.

Other names: Higman-Janko-McKay group, HJM

Remarks: J3 seems unrelated to any other sporadic groups (or to anything else). Its triple cover has a 9 dimensional unitary representation over the field with 4 elements.

[edit] Janko group J4

Order: 221 · 33 · 5 · 7 · 113 · 23 · 29 · 31 · 37 · 43 = 86775571046077562880

Schur multiplier: Trivial.

Outer automorphism group: Trivial.

Remarks: Has a 112 dimensional representation over the field with 2 elements.

[edit] Conway group Co1

Order: 221 · 39 · 54 · 72 · 11 · 13 · 23 = 4157776806543360000

Schur multiplier: Order 2.

Outer automorphism group: Trivial.

Other names: ·1

Remarks: The perfect double cover of Co1 is the automorphism group of the Leech lattice, and is sometimes denoted by ·0.

[edit] Conway group Co2

Order: 218 · 36 · 53 · 7 · 11 · 23 = 42305421312000

Schur multiplier: Trivial.

Outer automorphism group: Trivial.

Other names: ·2

Remarks: Subgroup of Co1; fixes a norm 4 vector in the Leech lattice.

[edit] Conway group Co3

Order: 210 · 37 · 53 · 7 · 11 · 23 = 495766656000

Schur multiplier: Trivial.

Outer automorphism group: Trivial.

Other names: ·3

Remarks: Subgroup of Co1; fixes a norm 6 vector in the Leech lattice.

[edit] Fischer group Fi22

Order: 217 · 39 · 52 · 7 · 11 · 13 = 64561751654400.

Schur multiplier: Order 6.

Outer automorphism group: Order 2.

Other names: M(22)

Remarks: A 3-transposition group whose double cover is contained in Fi23.

[edit] Fischer group Fi23

Order: 218 · 313 · 52 · 7 · 11 · 13 · 17 · 23 = 4089470473293004800.

Schur multiplier: Trivial.

Outer automorphism group: Trivial.

Other names: M(23)

Remarks: A 3-transposition group contained in Fi24.

[edit] Fischer group Fi24

Order: 221 · 316 · 52 · 73 · 11 · 13 · 17 · 23 · 29 = 1255205709190661721292800.

Schur multiplier: Order 3.

Outer automorphism group: Order 2.

Other names: M(24)′, F3+.

Remarks: The triple cover is contained in the monster group.

[edit] Higman-Sims group HS

Order: 29 · 32 · 53· 7 · 11 = 44352000

Schur multiplier: Order 2.

Outer automorphism group: Order 2.

Remarks: It acts as a rank 3 permutation group on the Higman Sims graph with 100 points, and is contained in Co3.

[edit] McLaughlin group McL

Order: 27 · 36 · 53· 7 · 11 = 898128000

Schur multiplier: Order 3.

Outer automorphism group: Order 2.

Remarks: Acts as a rank 3 permutation group on the McLauglin graph with 275 points, and is contained in Co3.

[edit] Held group He

Order: 210 · 33 · 52· 73· 17 = 4030387200

Schur multiplier: Trivial.

Outer automorphism group: Order 2.

Other names: Held-Higman-McKay group, HHM, F7

Remarks: Centralizes an element of order 7 in the monster group.

[edit] Rudvalis group Ru

Order: 214 · 33 · 53· 7 · 13 · 29 = 145926144000

Schur multiplier: Order 2.

Outer automorphism group: Trivial.

Remarks: The double cover acts on a 28 dimensional lattice over the Gaussian integers.

[edit] Suzuki sporadic group Suz

Order: 213 · 37 · 52· 7 · 11 · 13 = 448345497600

Schur multiplier: Order 6.

Outer automorphism group: Order 2.

Other names: Sz

Remarks: The 6 fold cover acts on a 12 dimensional lattice over the Eisenstein integers. It is not related to the Suzuki groups of Lie type.

[edit] O'Nan group O'N

Order: 29 · 34 · 5 · 73 · 11 · 19 · 31 = 460815505920

Schur multiplier: Order 3.

Outer automorphism group: Order 2.

Other names: O'Nan-Sims group, O'NS

Remarks: The triple cover has two 45-dimensional representations over the field with 7 elements, exchanged by an outer automorphism.

[edit] Harada-Norton group HN

Order: 214 · 36 · 56 · 7 · 11 · 19 = 273030912000000

Schur multiplier: Trivial.

Outer automorphism group: Order 2.

Other names: F5, D

Remarks: Centralizes an element of order 5 in the monster group.

[edit] Lyons group Ly

Order: 28 · 37 · 56 · 7 · 11 · 31 · 37 · 67 = 51765179004000000

Schur multiplier: Trivial.

Outer automorphism group: Trivial.

Other names: Lyons-Sims group, LyS

Remarks: Has a 111 dimensional representation over the field with 5 elements.

[edit] Thompson group Th

Order: 215 · 310 · 53 · 72 · 13 · 19 · 31 = 90745943887872000

Schur multiplier: Trivial.

Outer automorphism group: Trivial.

Other names: F3, E

Remarks: Centralizes an element of order 3 in the monster, and is contained in E8(3).

[edit] Baby Monster group B

Order:

   241 · 313 · 56 · 72 · 11 · 13 · 17 · 19 · 23 · 31 · 47
= 4154781481226426191177580544000000

Schur multiplier: Order 2.

Outer automorphism group: Trivial.

Other names: F2

Remarks: The double cover is contained in the monster group.

[edit] Fischer-Griess Monster group M

Order:

   246 · 320 · 59 · 76 · 112 · 133 · 17 · 19 · 23 · 29 · 31 · 41 · 47 · 59 · 71
= 808017424794512875886459904961710757005754368000000000

Schur multiplier: Trivial.

Outer automorphism group: Trivial.

Other names: F1, M1, Monster group, Friendly giant, Fischer's monster.

Remarks: Contains all but 6 of the other sporadic groups as subquotients. Related to monstrous moonshine. The monster is the automorphism group of the 196884 dimensional Griess algebra and the infinite dimensional monster vertex operator algebra, and acts naturally on the monster Lie algebra.

[edit] Non-cyclic simple groups of small order

Order Factorized order Group Schur multiplier Outer automorphism group
60 22 · 3 · 5 A5 = A1(4) = A1(5) 2 2
168 23 · 3 · 7 A1(7) = A2(2) 2 2
360 23 · 32 · 5 A6 = A1(9) = B2(2)′ 6 2×2
504 23 · 32 · 7 A1(8) = 2G2(3)′ 1 3
660 22 · 3 · 5 · 11 A1(11) 2 2
1092 22 · 3 · 7 · 13 A1(13) 2 2
2448 24 · 32 · 17 A1(17) 2 2
2520 23 · 32 · 5 · 7 A7 6 2
3420 22 · 32 · 5 · 19 A1(19) 2 2
4080 24 · 3 · 5 · 17 A1(16) 1 4
5616 24 · 33 · 13 A2(3) 1 2
6048 25 · 33 · 7 2A2(9) = G2(2)′ 1 2
6072 23 · 3 · 11 · 23 A1(23) 2 2
7800 23 · 3 · 52 · 13 A1(25) 2 2×2
7920 24 · 32 · 5 · 11 M11 1 1
9828 22 · 33 · 7 · 13 A1(27) 2 6

See also: List of small groups

[edit] Further reading

  • Daniel Gorenstein, Richard Lyons, Ronald Solomon The Classification of the Finite Simple Groups (volume 1), AMS, 1994 (volume 2), AMS,
  • Conway, J. H.; Curtis, R. T.; Norton, S. P.; Parker, R. A.; and Wilson, R. A.: "Atlas of Finite Groups: Maximal Subgroups and Ordinary Characters for Simple Groups." Oxford, England 1985.
  • Atlas of Finite Group Representations: contains representations and other data for many finite simple groups, including the sporadic groups.
  • Simple Groups of Lie Type by Roger W. Carter, ISBN 0-471-50683-4
  • Mark Ronan, Symmetry and the Monster, Oxford University Press, 2006. (Concise introduction and history written for lay reader)
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