OFFSET
0,5
FORMULA
a(n) = (n!)^2 * Sum_{k=0..floor(n/4)} |Stirling1(n-3*k,k)|/( (n-3*k)! * (n-k+1)! ).
E.g.f.: (1/x) * Series_Reversion( x/(1 - x^3*log(1 - x)) ).
PROG
(PARI) a(n) = n!^2*sum(k=0, n\4, abs(stirling(n-3*k, k, 1))/((n-3*k)!*(n-k+1)!));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Sep 19 2024
STATUS
approved