A375827 E.g.f. satisfies A(x) = exp(x^2 * (exp(x*A(x)) - 1)).
1, 0, 0, 6, 12, 20, 1110, 10122, 58856, 1239912, 23773770, 303367790, 5442263772, 135931189836, 2868815413646, 61708462976370, 1696559552295120, 48121891688969552, 1323641220801211026, 40678367069424137814, 1372011621943725532100
Offset: 0
Keywords
Programs
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PARI
a(n) = n!*sum(k=0, n\3, (n-2*k+1)^(k-1)*stirling(n-2*k, k, 2)/(n-2*k)!);
Formula
a(n) = n! * Sum_{k=0..floor(n/3)} (n-2*k+1)^(k-1) * Stirling2(n-2*k,k)/(n-2*k)!.