OFFSET
0,4
LINKS
Eric Weisstein's World of Mathematics, Lambert W-Function.
FORMULA
a(n) = n! * Sum_{k=1..floor(n/3)} k^(k-1) * Stirling2(n-2*k,k)/(2^k * (n-2*k)!).
PROG
(PARI) my(N=30, x='x+O('x^N)); concat([0, 0, 0], Vec(serlaplace(-lambertw(x^2/2*(1-exp(x))))))
(PARI) a(n) = n!*sum(k=1, n\3, k^(k-1)*stirling(n-2*k, k, 2)/(2^k*(n-2*k)!));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Sep 24 2022
STATUS
approved