OFFSET
0,6
FORMULA
a(n) = Sum_{k=1..floor(n/4)} (4*k)! * |Stirling1(n,4*k)|/(k * 24^k).
a(n) = |Stirling1(n,4)| + Sum_{k=1..n-1} |Stirling1(k,4)| * binomial(n-1,k) * a(n-k).
PROG
(PARI) a(n) = sum(k=1, n\4, (4*k)!*abs(stirling(n, 4*k, 1))/(k*24^k));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jan 23 2025
STATUS
approved
