A062824 a(n) = Ch(A005117(n)) where Ch(n) is Chowla's function and A005117(n) are the squarefree numbers.

0, 0, 0, 0, 5, 0, 7, 0, 0, 9, 8, 0, 0, 10, 13, 0, 15, 0, 41, 0, 14, 19, 12, 0, 21, 16, 0, 53, 0, 25, 0, 20, 0, 16, 22, 31, 0, 0, 33, 18, 77, 0, 26, 73, 0, 0, 39, 18, 89, 0, 43, 0, 22, 45, 32, 0, 20, 34, 49, 24, 0, 0, 113, 0, 86, 55, 0, 0, 105, 40, 0, 125, 28, 61, 24, 63, 44, 0, 46, 121, 0, 26, 69, 0, 149, 0, 50, 73, 24, 34, 75, 0

Offset: 1

Author

Jason Earls, Jul 20 2001

Keywords

• easy
• nonn

Links

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

Crossrefs

Cf. A005117, A048050.

Programs

Mathematica

chowla[n_] := DivisorSigma[1, n] - n - 1; chowla[1] = 0; chowla /@ Select[Range[150], SquareFreeQ] (* Amiram Eldar, Mar 10 2024 *)

PARI

j=[0]; for(n = 2, 150, if(issquarefree(n), j = concat(j, sigma(n)-n-1))); j

Formula

a(n) = A048050(A005117(n)). - Amiram Eldar, Mar 10 2024

Extensions

a(1) corrected by Amiram Eldar, Mar 10 2024