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A074628
Numbers k such that sigma(k) == 2 mod 6.
9
7, 13, 19, 21, 28, 31, 37, 39, 43, 52, 57, 61, 63, 67, 73, 76, 79, 84, 93, 97, 103, 109, 111, 112, 117, 124, 127, 129, 139, 148, 151, 156, 157, 163, 171, 172, 175, 181, 183, 189, 193, 199, 201, 208, 211, 219, 223, 228, 229, 237, 241, 244, 252
OFFSET
1,1
LINKS
FORMULA
A000203(n) mod 6 = 2.
{n: A084301(n) = 2}. - R. J. Mathar, May 19 2020
EXAMPLE
For k=39: sigma(39) = 1+3+13+39 = 56 = 6*9 + 2.
MATHEMATICA
Select[Range[300], Mod[DivisorSigma[1, #], 6]==2&] (* Harvey P. Dale, Nov 14 2014 *)
PROG
(PARI) isok(n) = ((sigma(n) % 6) == 2); \\ Michel Marcus, Dec 19 2013
KEYWORD
easy,nonn
AUTHOR
Labos Elemer, Aug 26 2002
STATUS
approved