A371197 Expansion of e.g.f. 1/(1 + x^2 * log(1 - x - x^2)).
1, 0, 0, 6, 36, 160, 1980, 26208, 319200, 4587840, 79117920, 1455410880, 28807099200, 626767165440, 14748882115968, 370481625360000, 9936445454208000, 283810433412280320, 8586642168981642240, 274263310453720412160, 9227500416766453248000
Offset: 0
Keywords
Programs
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PARI
a(n) = n!*sum(j=0, n, sum(k=0, j\2, k!*binomial(j-k, n-j-k)*abs(stirling(j-k, k, 1))/(j-k)!));
Formula
a(n) = n! * Sum_{j=0..n} Sum_{k=0..floor(j/2)} k! * binomial(j-k,n-j-k) * |Stirling1(j-k,k)|/(j-k)!.