OFFSET
0,3
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..350
FORMULA
a(n) = 5^n * n! * binomial((3*n+1)/5,n)/(3*n+1).
a(5*n+3) = 0.
MATHEMATICA
a[n_]:=If[n==0, 1, Product[(3* n+1-5 *k), {k, 0, n-1}]/(3 *n+1)]; Table[a[n], {n, 0, 25}] (* Vincenzo Librandi, Mar 26 2026 *)
PROG
(PARI) a(n) = 5^n*n!*binomial((3*n+1)/5, n)/(3*n+1);
(Magma) [n eq 0 select 1 else (5^n*&*[((3*n+1)/5-k): k in [0..n-1] ])/(3*n+1): n in [0..23]]; // Vincenzo Librandi, Mar 26 2026
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Seiichi Manyama, Mar 24 2026
STATUS
approved
