A373523 Expansion of e.g.f. exp(x * (1 + x^3)^(2/3)).
1, 1, 1, 1, 17, 81, 241, 1, 5601, 62497, 518561, 313281, 3999601, -40669199, 2177551377, 7318933441, 397613245121, -1411251083199, 9245424513601, -1554110065897343, 8222970963680721, 2117868896399761, 11780583339147607601, -55331596875625839999
Offset: 0
Keywords
Programs
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PARI
a(n) = n!*sum(k=0, n\3, binomial(2*n/3-2*k, k)/(n-3*k)!);
Formula
a(n) = n! * Sum_{k=0..floor(n/3)} binomial(2*n/3-2*k,k)/(n-3*k)!.
a(n) == 1 mod 16.