Maekawa's theorem
A flat-folded crease pattern with one vertex, five mountain folds (the folds with the colored side outside and the white side inside) and three valley folds (with the white side on the outside of the fold)
Maekawa's theorem is a theorem in the mathematics of paper folding named after Jun Maekawa. It relates to flat-foldable origami crease patterns and states that at every vertex, the numbers of valley and mountain folds always differ by two in either direction.