A070610 Number of positive integers k such that sigma(k) divides sigma(n).

1, 2, 2, 2, 3, 6, 3, 3, 2, 5, 6, 5, 3, 10, 10, 3, 5, 4, 3, 8, 5, 9, 10, 12, 3, 8, 5, 8, 5, 18, 5, 4, 13, 7, 13, 4, 2, 12, 8, 10, 8, 19, 3, 15, 6, 18, 13, 7, 3, 5, 18, 5, 7, 21, 18, 21, 7, 10, 12, 27, 4, 19, 6, 2, 15, 26, 3, 13, 19, 26, 18, 6, 2, 7, 7, 8, 19, 27, 7, 9, 2, 13, 15, 14, 13, 9

Offset: 1

Author

Benoit Cloitre, May 13 2002

Keywords

• easy
• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..16384
• Index entries for sequences related to sigma(n)

Crossrefs

Cf. A000203, A070242, A071181, A074754.

Programs

PARI

for(n=1,150,print1(sum(i=1,10*n,if((sigma(n))%(sigma(i)),0,1)),","))

PARI

A070610(n) = { my(s=sigma(n)); sum(k=1, s, !(s%sigma(k))); }; \\ Antti Karttunen, Nov 17 2017

Formula

a(n) = A074754(A000203(n)). - Antti Karttunen, Nov 17 2017

Extensions

Offset corrected, name edited by Antti Karttunen, Nov 17 2017