OFFSET
0,2
FORMULA
a(n) = n*(n+3)*a(n-1) + 1.
a(n) ~ BesselI(3,2) * n! * (n+3)!. - Vaclav Kotesovec, Jan 09 2024
PROG
(PARI) a(n) = n!*(n+3)!*sum(k=0, n, 1/(k!*(k+3)!));
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Seiichi Manyama, Jan 07 2024
STATUS
approved