A248150 Numbers whose sum of divisors (A000203) is divisible by 4.

3, 6, 7, 11, 12, 14, 15, 19, 21, 22, 23, 24, 27, 28, 30, 31, 33, 35, 38, 39, 42, 43, 44, 46, 47, 48, 51, 54, 55, 56, 57, 59, 60, 62, 63, 65, 66, 67, 69, 70, 71, 75, 76, 77, 78, 79, 83, 84, 85, 86, 87, 88, 91, 92, 93, 94, 95, 96, 99, 102, 103, 105, 107, 108, 110, 111, 112, 114, 115, 118

Offset: 1

Author

M. F. Hasler, Oct 02 2014

Keywords

• nonn

Comments

A subsequence of A028983 (even sum of divisors) which contains all numbers but the squares and twice the squares, so no term of this sequence is of that form, either.

Any number having at least two odd prime factors to an odd power is in this sequence, therefore it has asymptotic density 1. - M. F. Hasler, Apr 26 2017

Links

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

Crossrefs

Cf. A000203, A028982, A028983, A248151.

First differs from A022544 by including 65.

Programs

Mathematica

Select[Range[200],Divisible[DivisorSigma[1,#],4]&] (* Harvey P. Dale, Feb 20 2015 *)

PARI

for(n=1,999,sigma(n)%4||print1(n","))

Formula

a(n) ~ n. - Charles R Greathouse IV, Sep 01 2015