Euler's rule
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Euler's rule, named after Leonhard Euler, is a generalization of Thâbit ibn Kurrah rule for finding amicable numbers. If a = 2m×(2n-m + 1) - 1, b = 2n×(2n-m + 1) - 1, and c = 2n+m×(2n-m + 1)2 - 1 are all prime, for integers 0 < m < n, then 2n × a × b and 2n × c are amicable. This hypothesis is satisfied for the pairs (m,n) = (1,2), (3,4), (6,7), (1,8), and (29,40), but for no other pairs with n < 2500. The first three of these pairs yield the three pairs of amicable numbers discovered using the Thâbit ibn Kurrah rule.
[edit] See also
euler's rule is to do with solids but it only works with straight edges.it is F= faces + V= veticites - E= edges and its will also = 2. eg. if a square pyramid has 4 faces and 8 verticies and 5 edges it will be 4F+8V-5E=2
