OFFSET
0,3
COMMENTS
Unlike the factorial number n!, a(n) does not have trailing zeros.
LINKS
Harvey P. Dale, Table of n, a(n) for n = 0..434
FORMULA
MATHEMATICA
Table[Product[Floor[(5k-1)/4], {k, n}], {n, 0, 22}] (* or *)
Join[{1}, Table[Floor[(5n-1)/4]!/(Floor[Floor[(5n-1)/4]/5]!*5^Floor[Floor[(5n-1)/4]/5]), {n, 22}]]
Join[{1}, FoldList[Times, Table[If[Mod[n, 5]==0, Nothing, n], {n, 30}]]] (* Harvey P. Dale, Nov 03 2024 *)
PROG
(Python)
from math import prod
def a(n): return prod((5*k-1)//4 for k in range(1, n+1))
print([a(n) for n in range(23)]) # Michael S. Branicky, Sep 01 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Stefano Spezia, Sep 01 2022
STATUS
approved