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 A074628 Numbers k such that sigma(k) == 2 mod 6. 8
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 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 CROSSREFS Cf. A000203, A072862, A074384, A074627, A074628, A074629, A074630. Sequence in context: A160007 A024613 A024606 * A232436 A274437 A031194 Adjacent sequences:  A074625 A074626 A074627 * A074629 A074630 A074631 KEYWORD easy,nonn AUTHOR Labos Elemer, Aug 26 2002 STATUS approved

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Last modified May 6 19:52 EDT 2021. Contains 343586 sequences. (Running on oeis4.)