A375830 E.g.f. satisfies A(x) = 1/(1 - x^2*A(x))^x.
1, 0, 0, 6, 0, 60, 1080, 1680, 80640, 1058400, 8316000, 257463360, 3692304000, 66421555200, 1801442522880, 34333457558400, 905811504998400, 25171307671910400, 646170363904665600, 20523302430017587200, 637272191855819520000, 20620406757762459648000
Offset: 0
Keywords
Crossrefs
Cf. A375831.
Programs
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PARI
a(n) = n!*sum(k=0, n\2, (k+1)^(n-2*k-1)*abs(stirling(k, n-2*k, 1))/k!);
Formula
a(n) = n! * Sum_{k=0..floor(n/2)} (k+1)^(n-2*k-1) * |Stirling1(k,n-2*k)|/k!.