OFFSET
0,2
LINKS
Harvey P. Dale, Table of n, a(n) for n = 0..203
FORMULA
a(n) = binomial(n+2,3)*a(n-1) + 1.
MATHEMATICA
nxt[{n_, a_}]:={n+1, a*Binomial[n+3, 3]+1}; NestList[nxt, {0, 1}, 20][[;; , 2]] (* Harvey P. Dale, May 26 2024 *)
PROG
(PARI) a(n) = n!*(n+1)!*(n+2)!*sum(k=0, n, 1/(6^(n-k)*k!*(k+1)!*(k+2)!));
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Seiichi Manyama, Jan 07 2024
STATUS
approved