Triangle read by rows: T(n,k) is the number of involutions of {1,2,...,n} having k descents (n>=1; 0<=k
1, 1, 1, 1, 2, 1, 1, 4, 4, 1, 1, 6, 12, 6, 1, 1, 9, 28, 28, 9, 1, 1, 12, 57, 92, 57, 12, 1, 1, 16
1 seqfan posts
Tue Nov 9 20:02:15 CET 2010 [seqfan] Re: A180388-A180389 pops up in unexpected place (Re: PS: Permutation Ascents )