0, 1, 0, 1, 2, 0, 2, 8, 0, 4, 0, 24, 0, 12, 0, 108, 0, 36, 576, 0, 720, 0, 144, 4608, 0, 4032, 0, 576, 0, 31680, 0, 31680, 0, 2880, 0, 288000, 0, 201600, 0, 14400, 2505600, 0, 2764800, 0, 1987200, 0, 86400, 30067200, 0, 28512000, 0, 14515200, 0, 518400
Offset: 1
Triangle begins
0, 1;
0, 1;
2, 0, 2;
8, 0, 4;
0, 24, 0, 12;
0, 108, 0, 36;
576, 0, 720, 0, 144;
4608, 0, 4032, 0, 576;
0, 31680, 0, 31680, 0, 2880;
0, 288000, 0, 201600, 0, 14400;
2505600, 0, 2764800, 0, 1987200, 0, 86400;
30067200, 0, 28512000, 0, 14515200, 0, 518400;
The compressed triangle resulting from the division of each entry by the last entry of its row begins as follows. If i is the index of the row, starting with i = 1 then this last entry is floor(i/2)! * (i - floor(i/2))!.
0, 1;
0, 1;
1, 0, 1;
2, 0, 1;
0, 2, 0, 1;
0, 3, 0, 1;
4, 0, 5, 0, 1;
8, 0, 7, 0, 1;
0, 11, 0, 11, 0, 1;
0, 20, 0, 14, 0, 1;
29, 0, 32, 0, 23, 0, 1;
58, 0, 55, 0, 28, 0, 1;
0, 88, 0, 94, 0, 46, 0, 1;
0, 169, 0, 146, 0, 53, 0, 1;
263, 0, 282, 0, 283, 0, 86, 0, 1;
526, 0, 515, 0, 383, 0, 97, 0, 1;
For the sense of the entries of this triangle see the [Shevelev] link (with a continuation there). Let B(n,i) be the set of permutations C of 1..n for which c_1 - c_2 + ... + (-1)^(n-1)*c_n = i^2, i >= 0. Then |B(n,i)| is the entry in the n-th row and i-th column of the first triangle. Let us call two permutations C_1 and C_2 equivalent if one of them is obtained from another by a permutation of its elements with odd indices and/or separately with even indices. Let b(n,i) be the entry in the n-th row and i-th column of the second triangle. Then b(n,i) is the maximal possible number of pairwise non-equivalent permutations which could be chosen in B(n,i). On the other hand, it is the smallest number of non-equivalent permutations in B(n,i) such that every other permutation in B(n,i) is equivalent to one of them. So in some sense b(n,i) is the dimension of B(n,i). In particular, b(n,i) = 0 corresponds to empty B(n,i). - _Vladimir Shevelev_, Nov 13 2017
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