OFFSET
0,4
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..10000
FORMULA
EXAMPLE
The a(1) = 1 through a(8) = 12 divisors:
1 1 1 1 1 1 1 1
3 3 3 3 3 3
5 5 5 5
15 9 7 7
15 9 9
45 15 15
21 21
35 35
45 45
63 63
105 105
315 315
MATHEMATICA
Table[Length[Select[Divisors[n!], OddQ]], {n, 0, 15}]
PROG
(PARI) a(n) = sumdiv(n!, d, d%2); \\ Michel Marcus, Aug 24 2020
(PARI) a(n) = numdiv(prod(k=1, n, k >> valuation(k, 2))); \\ Michel Marcus, Aug 27 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Aug 23 2020
EXTENSIONS
a(36)-a(44) from Seiichi Manyama, Aug 26 2020
STATUS
approved