A136535 A128064 * A001263.
1, 1, 2, 1, 7, 3, 1, 15, 21, 4, 1, 26, 76, 46, 5, 1, 40, 200, 250, 85, 6, 1, 57, 435, 925, 645, 141, 7, 1, 77, 833, 2695, 3185, 1421, 217, 8, 1, 100, 1456, 6664, 11956, 9016, 2800, 316, 9, 1, 126, 2376, 14616, 37044, 42336, 22176, 5076, 441, 10
Offset: 1
Examples
First few rows of the triangle are: 1; 1, 2; 1, 7, 3; 1, 15, 21, 4; 1, 26, 76, 46, 5; 1, 40, 200, 250, 85, 6; 1, 57, 435, 925, 645, 141, 7; ...
Programs
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PARI
T4(n,k) = sum(j=k, n, binomial(n,j)*binomial(j,k)*(-1)^(j-k)*(j+1)); T3(n,k) = binomial(n, k)*binomial(n-1, k-1) - binomial(n, k-1)*binomial(n-1, k); N=10; matrix(N, N, n, k, T4(n-1,k-1))*matrix(N, N,n,k,T3(n,k)) \\ Michel Marcus, Oct 11 2021
Extensions
a(18) corrected by Georg Fischer, Oct 10 2021
Comments