A354038 Numbers k such that sum of the proper divisors of k is a multiple of 4.

1, 9, 10, 12, 24, 26, 28, 34, 44, 48, 49, 56, 58, 60, 74, 76, 81, 82, 84, 88, 90, 92, 96, 106, 108, 112, 120, 121, 122, 124, 132, 140, 146, 152, 156, 168, 172, 176, 178, 184, 188, 192, 194, 202, 204, 216, 218, 220, 224, 226, 228, 234, 236, 240, 248, 252, 260, 264, 268, 274, 276, 280, 284, 298, 300, 304, 306, 308

Offset: 1

Author

Antti Karttunen, May 16 2022

Keywords

• nonn

Comments

Numbers k for which A001065(k) = 4*m for some m.

Links

• Index entries for sequences related to sigma(n)

Crossrefs

Cf. A000203, A001065, A010873, A105824, A354037 (characteristic function).

Programs

Mathematica

Select[Range[300], Divisible[DivisorSigma[1, #] - #, 4] &] (* Amiram Eldar, May 16 2022 *)

PARI

A354037(n) = (0==((sigma(n)-n)%4));
isA354038(n) = A354037(n);

Formula

{k | A010873(k) == A105824(k)}.