A067696 - OEIS

%I #22 Feb 24 2021 09:03:29

%S 1,5,13,15,31,39,49,96,111,205,215,452,492,712,1258,5599,10170,11514,

%T 32844,58841,59550,83251,83650,115139,120485,144835,152583,467583,

%U 709178,1617217,3101711,3554345,3714335,6580179,8099488

%N Numbers k such that prime(k) == -1 (mod sigma(k)).

%t Do[s=(Prime[n]+1)/DivisorSigma[1, n]; If[IntegerQ[s], Print[n]], {n, 1000000, 10000000}

%t Select[Range[81*10^5],Mod[Prime[#]+1,DivisorSigma[1,#]]==0&] (* _Harvey P. Dale_, May 03 2018 *)

%Y Cf. A067697, A071170.

%K nonn

%O 1,2

%A _Benoit Cloitre_, Feb 05 2002

%E More terms from _Labos Elemer_, Jun 12 2003