A325311 Odd abundant numbers k for which sigma(k) == 3 (mod 4).

11025, 99225, 245025, 540225, 893025, 1334025, 2205225, 3980025, 4862025, 5832225, 6890625, 8037225, 8555625, 9828225, 10595025, 10989225, 12006225, 14402025, 19847025, 20385225, 24354225, 26163225, 26471025, 29648025, 31979025, 35820225, 38378025, 43758225, 46580625, 49491225, 50339025, 52490025, 55577025, 57836025, 60140025

Offset

1,1

Comments

These are all squares. Square roots are in A325312.

Links

Antti Karttunen, Table of n, a(n) for n = 1..10000

Index entries for sequences related to sigma(n).

Formula

a(n) = A325312(n)^2. - Amiram Eldar, Apr 05 2024

Mathematica

Select[Range[1, 7755, 2]^2, Mod[(s = DivisorSigma[1, #]), 4] == 3 && s > 2*# &] (* Amiram Eldar, Apr 05 2024 *)

Prog

(PARI) isA325311(n) = (n%2 && (3==sigma(n)%4) && sigma(n)>(2*n));

Crossrefs

Cf. A000203, A324647, A325312 (square roots).

Intersection of A005231 and A324899.

Subsequence of A156942.

Sequence in context: A129087 A239828 A156942 * A164518 A198208 A139409

Adjacent sequences: A325308 A325309 A325310 * A325312 A325313 A325314

Keyword

nonn

Author

Antti Karttunen, Apr 20 2019

Status

approved