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A072461 Sigma(n) == 1 mod 4. 5
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified December 8 17:01 EST 2021. Contains 349596 sequences. (Running on oeis4.)