OFFSET
1
COMMENTS
First differs from A295884 at n = 128.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
EXAMPLE
a(16) = 1 since 16 has 1 nonunitary divisor that is a cube, 8 = 2^3.
a(128) = 2 since 128 has 2 nonunitary divisors that are cubes, 8 = 2^3 and 64 = 4^3.
MATHEMATICA
f1[p_, e_] := 1 + Floor[e/3]; f2[p_, e_] := 2^If[Divisible[e, 3], 1, 0]; a[1] = 0; a[n_] := Times @@ f1 @@@ (fct = FactorInteger[n])- Times @@ f2 @@@ fct; Array[a, 100]
PROG
(PARI) a(n) = {my(f = factor(n)); prod(i = 1, #f~, 1 + f[i, 2]\3) - prod(i = 1, #f~, 2^if(f[i, 2]%3, 0, 1)); }
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Amiram Eldar, Jan 23 2025
STATUS
approved