OFFSET
0,5
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..1000
FORMULA
a(n) = (3 * a(n-1) + n * a(n-4) + 1)/4 for n > 3.
PROG
(PARI) a(n) = sum(k=0, n\4, (n-3*k)!/(n-4*k)!);
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Seiichi Manyama, Nov 19 2022
STATUS
approved