A072461 Sigma(n) == 1 mod 4.

1, 9, 49, 50, 81, 100, 121, 200, 338, 361, 400, 441, 450, 529, 578, 625, 676, 729, 800, 900, 961, 1089, 1156, 1352, 1600, 1682, 1800, 1849, 2209, 2312, 2401, 2450, 2704, 2738, 3042, 3200, 3249, 3362, 3364, 3481, 3600, 3969, 4050, 4225, 4489, 4624, 4761

Offset

1,2

Links

Ray Chandler, Table of n, a(n) for n = 1..10000 (first 1000 terms from Harvey P. Dale)

Mathematica

Select[Range[5000], Mod[DivisorSigma[1, #], 4]==1&] (* Harvey P. Dale, Oct 24 2016 *)

Prog

(PARI) isok(n) = ((sigma(n) % 4) == 1);

Crossrefs

Cf. A000203, A028982, A072462.

Sequence in context: A283092 A249780 A140891 * A181607 A012260 A262537

Adjacent sequences: A072458 A072459 A072460 * A072462 A072463 A072464

Keyword

nonn

Author

Labos Elemer, Jun 19 2002

Extensions

Name edited by Michel Marcus, Dec 19 2013

Status

approved