**Number of key permutations of length n: permutations {a_i} with |a_i-a_{i-1}|=1 or 2.**

*1, 2, 6, 12, 20, 34, 56, 88, 136, 208, 314, 470, 700, 1038, 1534, 2262, 3330, 4896*

*1 seqfan posts*

Index of A-numbers in seqfan: by ascending order by month by frequency by keyword

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