OFFSET
1,4
COMMENTS
By convention a(1) = 1.
Values can be 1, 3, 6, 9, 10, 15, 18, 21, 27, 28, 30, 36, 45, 54, 60, 63, 84, 90, etc. - Robert G. Wilson v, Dec 10 2017
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
The a(256) = 10 ways are:
(2^1)^8 (2^2)^4 (2^4)^2 (2^8)^1
(4^1)^4 (4^2)^2 (4^4)^1
(16^1)^2 (16^2)^1
(256^1)^1
MAPLE
f:= proc(n) local m, d, t;
m:= igcd(seq(t[2], t=ifactors(n)[2]));
add(numtheory:-tau(d), d=numtheory:-divisors(m))
end proc:
f(1):= 1:
map(f, [$1..100]); # Robert Israel, Dec 19 2017
MATHEMATICA
Table[Sum[DivisorSigma[0, d], {d, Divisors[GCD@@FactorInteger[n][[All, 2]]]}], {n, 100}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Nov 29 2017
STATUS
approved