A375833 E.g.f. satisfies A(x) = 1/(1 - x*(exp(x^2*A(x)) - 1)).
1, 0, 0, 6, 0, 60, 1440, 840, 100800, 1829520, 6350400, 419459040, 7125148800, 72657224640, 3691516308480, 66691652227200, 1362335156582400, 60600254383468800, 1285478183493504000, 40463468995171622400, 1701073478756171520000
Offset: 0
Keywords
Crossrefs
Cf. A371304.
Programs
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PARI
a(n) = n!*sum(k=0, n\2, (n-k)!*stirling(k, n-2*k, 2)/(k!*(k+1)!));
Formula
a(n) = n! * Sum_{k=0..floor(n/2)} (n-k)! * Stirling2(k,n-2*k)/( k! * (k+1)! ).