OFFSET
0,3
FORMULA
a(n) = Sum_{k=0..n} (3*n-2*k)!/(3*n-3*k+1)! * |Stirling1(n,k)|.
PROG
(PARI) a(n) = sum(k=0, n, (3*n-2*k)!/(3*n-3*k+1)!*abs(stirling(n, k, 1)));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Nov 08 2023
STATUS
approved