OFFSET
0,3
FORMULA
a(n) = Sum_{k=1..n} (n+3*k-2)!/(n+2*k-1)! * Stirling1(n,k).
E.g.f.: Series_Reversion( (1 - x) * (exp(x * (1 - x)^2) - 1) ). - Seiichi Manyama, Sep 09 2024
PROG
(PARI) a(n) = sum(k=1, n, (n+3*k-2)!/(n+2*k-1)!*stirling(n, k, 1));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Mar 19 2024
STATUS
approved