Combinatorially, the affine permutation s 1 has window notation [ 2 , 1 ] , corresponding to the bijection 2 k ↦ ↦ 2 k − − 1 , 2 k − − 1 ↦ ↦ 2 k for every integer k. The affine permutation s 0 has window notation [ 0 , 3 ] , corresponding to the bijection 2 k ↦ ↦ 2 k + 1 , 2 k + 1 ↦ ↦ 2 k for every integer k. Other elements have the following window notations: