A384030 a(n) = [x^(2*n)] Product_{k=0..n-1} (1 + k*x)^4.
1, 0, 1, 248, 79441, 38878520, 27741179521, 27412462941136, 35965398129639713, 60588665662486807184, 127588718827126433989569, 328596587850349392471155720, 1016488989627693108972046560497, 3720090951049096346043302894560648, 15901046580509525131539058273675597889
Offset: 0
Keywords
Programs
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PARI
a(n) = sum(i=0, n, sum(j=0, 2*n-i, sum(k=0, 2*n-i-j, abs(stirling(n, i, 1)*stirling(n, j, 1)*stirling(n, k, 1)*stirling(n, 2*n-i-j-k, 1)))));
Formula
a(n) = Sum_{0<=i, j, k, l<=n and i+j+k+l=2*n} |Stirling1(n,i) * Stirling1(n,j) * Stirling1(n,k) * Stirling1(n,l)|.