OFFSET
1,2
COMMENTS
a(n) depends only on the prime signature of n.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..300
FORMULA
For prime p, a(p^n) = A000124(n) (independently of p).
a(n) = A069625(n) + 1. - Michel Marcus, Sep 17 2013
EXAMPLE
For n=4, n has factors 1, 2, and 4, which can be multiplied to yield 1, 2, 4, or 8, thus a(4)=4.
MATHEMATICA
a[n_] := Length[DeleteDuplicates[Times @@@ Subsets[Divisors[n]]]]; Table[a[n], {n, 100}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ben Branman, Feb 27 2012
STATUS
approved