OFFSET
0,2
FORMULA
a(n) = Sum_{k=0..3} k! * binomial(3,k) * Stirling1(n,k).
a(0) = 1; a(n) = Sum_{k=1..n} (-1)^(k-1) * (4 * k/n - 1) * (k-1)! * binomial(n,k) * a(n-k).
PROG
(PARI) a(n) = sum(k=0, 3, k!*binomial(3, k)*stirling(n, k, 1));
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Seiichi Manyama, Oct 27 2024
STATUS
approved