OFFSET
1,6
EXAMPLE
The a(60) = 8 ways to write 60 as a product of two numbers, neither of which is a perfect power, are 2*30, 3*20, 5*12, 6*10, 10*6, 12*5, 20*3, 30*2.
MATHEMATICA
radQ[n_]:=And[n>1, GCD@@FactorInteger[n][[All, 2]]===1];
Table[Length[Select[Divisors[n], radQ[#]&&radQ[n/#]&]], {n, 100}]
PROG
(PARI) ispow(n) = (n==1) || ispower(n);
a(n) = sumdiv(n, d, !ispow(d) && !ispow(n/d)); \\ Michel Marcus, May 17 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, May 15 2018
STATUS
approved