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 A076496 Numbers n such that sigma(n) == 12 (mod n). 10
 1, 24, 30, 42, 54, 66, 78, 102, 114, 121, 138, 174, 186, 222, 246, 258, 282, 304, 318, 354, 366, 402, 426, 438, 474, 498, 534, 582, 606, 618, 642, 654, 678, 762, 780, 786, 822, 834, 894, 906, 942, 978, 1002, 1038, 1074, 1086, 1146, 1158, 1182, 1194, 1266, 1338 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS These numbers are also solutions of the equation: g[n]:=2n+1-sigma[n]=-11 (or they are cofacient numbers of type -11). - Vassil K. Tintschev (tinchev(AT)sunhe.jinr.ru), Dec 15 2004 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 EXAMPLE 6p is a solution if p>3 is prime, since sigma[6p]=1+2+3+6+p+2p+3p+6p=12(p+1)=2.6p+12=2n+12. These are "regular" solutions. Also n=121,304 are "singular" solutions. See other remainders in cross-references. MATHEMATICA Do[s=Mod[DivisorSigma[1, n], n]; If[IntegerQ[n/1000000], Print[{n}]]; If[Equal[s, 12], Print[{n, n/6}]], {n, 1, 1000}] Join[{1}, Select[Range[2000], Mod[DivisorSigma[1, #], #]==12 &]] (* Vincenzo Librandi, Mar 11 2014 *) PROG (PARI) is(n)=sigma(n)%n==12 \\ Charles R Greathouse IV, Mar 09 2014 CROSSREFS Cf. A054024, A045768, A045769, A045770, A076495, A076496, A088834. Sequence in context: A030626 A302571 A125639 * A125640 A141545 A106682 Adjacent sequences:  A076493 A076494 A076495 * A076497 A076498 A076499 KEYWORD nonn AUTHOR Labos Elemer, Oct 21 2002 EXTENSIONS Initial term 1 added by Vincenzo Librandi, Mar 11 2014 STATUS approved

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Last modified March 29 02:19 EDT 2020. Contains 333104 sequences. (Running on oeis4.)