A160812 a(n) = A161205(n)-A000005(n).

0, 0, 0, 0, 2, 0, 2, 0, 2, 2, 4, 0, 4, 2, 2, 2, 6, 2, 6, 2, 4, 4, 6, 0, 6, 6, 6, 4, 8, 2, 8, 4, 6, 6, 6, 2, 10, 8, 8, 4, 10, 4, 10, 6, 6, 8, 10, 2, 10, 8, 10, 8, 12, 6, 10, 6, 10, 10, 12, 2, 12, 10, 8, 8, 12, 8, 14, 10, 12, 8, 14, 4, 14, 12, 10, 10, 12, 8, 14, 6, 12, 14, 16, 6, 14, 14, 14, 10, 16, 6

Offset: 1

Author

Omar E. Pol, Jun 19 2009

Keywords

• easy
• nonn

Comments

It appears that a(n)= 0 if and only if n divides 24 (See also the comments in A018253).

Links

• Omar E. Pol, Determinacion geometrica de los numeros primos y perfectos
• Omar E. Pol, Illustration: Divisors and pi(x)

Crossrefs

Cf. A000005, A000720, A018253, A160811, A161205.

Formula

a(n) = 2*(A000196(n) - A038548(n)) = 2*A236627(n). - Omar E. Pol, Feb 05 2014

Extensions

Edited by Omar E. Pol, Aug 02 2009