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A074629 Sigma(n) == 3 mod 6. 5
2, 8, 18, 32, 49, 50, 72, 98, 128, 162, 169, 196, 200, 242, 288, 338, 361, 392, 441, 450, 512, 578, 648, 676, 722, 784, 800, 882, 961, 968, 1058, 1152, 1225, 1250, 1352, 1369, 1444, 1458, 1521, 1568, 1682, 1764, 1800, 1849, 1922, 2048, 2178, 2312, 2450, 2592 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Square terms are in A074216. Nonsquare terms appear to be A001105 except {0}. - Michel Marcus, Dec 26 2013

In the prime factorization of n, no odd prime has odd exponent, and 2 has odd exponent or at least one prime == 1 (mod 6) has exponent == 2 (mod 6). - Robert Israel, Dec 11 2015

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

FORMULA

A000203(n) mod 6 = 3.

EXAMPLE

n=32: sigma(32) = 63 = 6*10 + 3.

MAPLE

select(t -> numtheory:-sigma(t) mod 6 = 3, [$1..10000]); # Robert Israel, Dec 11 2015

MATHEMATICA

Select[Range@ 2600, Mod[DivisorSigma[1, #], 6] == 3 &] (* Michael De Vlieger, Dec 10 2015 *)

PROG

(PARI) isok(n) = (sigma(n) % 6) == 3; \\ Michel Marcus, Dec 26 2013

(MAGMA) [n: n in [1..3*10^3] | (SumOfDivisors(n) mod 6) eq 3]; // Vincenzo Librandi, Dec 11 2015

CROSSREFS

Cf. A000203, A072862, A074384, A074627, A074628, A074630.

Appears to be the same sequence as A067051. - Ralf Stephan, Aug 18 2004

Sequence in context: A293296 A055044 A067051 * A209303 A001105 A051787

Adjacent sequences:  A074626 A074627 A074628 * A074630 A074631 A074632

KEYWORD

easy,nonn

AUTHOR

Labos Elemer, Aug 26 2002

STATUS

approved

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Last modified October 18 12:18 EDT 2019. Contains 328160 sequences. (Running on oeis4.)