A152674 Number of divisors of the numbers that are not squares.

2, 2, 2, 4, 2, 4, 4, 2, 6, 2, 4, 4, 2, 6, 2, 6, 4, 4, 2, 8, 4, 4, 6, 2, 8, 2, 6, 4, 4, 4, 2, 4, 4, 8, 2, 8, 2, 6, 6, 4, 2, 10, 6, 4, 6, 2, 8, 4, 8, 4, 4, 2, 12, 2, 4, 6, 4, 8, 2, 6, 4, 8, 2, 12, 2, 4, 6, 6, 4, 8, 2, 10, 4, 2, 12, 4, 4, 4, 8, 2, 12, 4, 6, 4, 4, 4, 12, 2, 6, 6, 2, 8, 2, 8

Offset: 1

Author

Omar E. Pol, Dec 10 2008

Keywords

• easy
• nonn

Comments

Even members of A000005.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000005, A000037, A095686.

Programs

Mathematica

Select[DivisorSigma[0, Range[100]], EvenQ] (* Amiram Eldar, Dec 02 2023 *)

PARI

lista(kmax) = for(k = 1, kmax, if(!issquare(k), print1(numdiv(k), ", "))); \\ Amiram Eldar, Dec 02 2023

Formula

a(n) = A000005(A000037(n)).

a(n) = 2*A095686(n). - Amiram Eldar, Dec 02 2023