OFFSET
0,3
FORMULA
a(n) = (2*n)! * Sum_{k=0..n} Stirling1(n,k)/(2*n-k+1)!.
PROG
(PARI) a(n) = (2*n)!*sum(k=0, n, stirling(n, k, 1)/(2*n-k+1)!);
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Nov 07 2023
STATUS
approved