OFFSET
1,2
COMMENTS
a(2n-1) = 1.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..1000
EXAMPLE
a(6) = 6: the divisors of 6 are 1, 2, 3 and 6 and the divisor products are 1, 2, 3, 6, 12, 18 and 36; the primes arising are 2, 3, 7, 13, 19 and 37.
a(12) = 11 = #{2, 3, 5, 7, 13, 19, 37, 73, 97, 433, 577}.
MATHEMATICA
Table[Count[Union[Times@@@Subsets[Divisors[n], DivisorSigma[0, n]]]+1, _?PrimeQ], {n, 100}] (* Harvey P. Dale, Jun 24 2013 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Jun 01 2003
EXTENSIONS
More terms from David Wasserman, Dec 28 2004
Corrected by Harvey P. Dale, Jun 24 2013
STATUS
approved