A326146 a(n) = sigma(n) - A020639(n) - n, where A020639 gives the smallest prime factor of n, and sigma is the sum of divisors of n.

-1, -1, -2, 1, -4, 4, -6, 5, 1, 6, -10, 14, -12, 8, 6, 13, -16, 19, -18, 20, 8, 12, -22, 34, 1, 14, 10, 26, -28, 40, -30, 29, 12, 18, 8, 53, -36, 20, 14, 48, -40, 52, -42, 38, 30, 24, -46, 74, 1, 41, 18, 44, -52, 64, 12, 62, 20, 30, -58, 106, -60, 32, 38, 61, 14, 76, -66, 56, 24, 72, -70, 121, -72, 38, 46, 62, 12, 88

Offset: 1

Author

Antti Karttunen, Jun 10 2019

Keywords

• sign

Links

• Antti Karttunen, Table of n, a(n) for n = 1..20000

Crossrefs

Cf. A000203, A001065, A020639, A061228, A105086, A326074, A326147, A326148.

Programs

PARI

A020639(n) = if(1==n, n, factor(n)[1, 1]);
A326146(n) = (sigma(n)-A020639(n)-n);

Formula

a(n) = A000203(n) - A020639(n) - n = A000203(n) - A061228(n).

a(n) = A001065(n) - A020639(n).

For n > 1, a(n) = A105086(n) - n.