OFFSET
0,2
FORMULA
a(n) = (1/2) * Sum_{k=0..n} 2^k * (k+2)! * Stirling2(n,k).
a(0) = 1; a(n) = 2*Sum_{k=1..n} (2*k/n + 1) * binomial(n,k) * a(n-k).
a(0) = 1; a(n) = 6*a(n-1) - 3*Sum_{k=1..n-1} (-1)^k * binomial(n-1,k) * a(n-k).
PROG
(PARI) a(n) = sum(k=0, n, 2^k*(k+2)!*stirling(n, k, 2))/2;
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Nov 19 2023
STATUS
approved