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%I #23 Mar 08 2024 01:14:20
%S 118,1558,2938,17758,19918,32218,33838,55963,71038,186778,308038,
%T 511498,523774,553498,699358,838213,1048903,1159378,1328938,1333246,
%U 1700038,2462686,2703886,2956078,3115318,3561094,3764206,3972694,7625878,7852918,8048962
%N Numbers k such that sigma(k+2) = 2*sigma(k).
%C a(1) = A175874(2).
%H Vincenzo Librandi and Donovan Johnson, <a href="/A175876/b175876.txt">Table of n, a(n) for n = 1..1000</a> (first 171 terms from Vincenzo Librandi)
%t Do[If[DivisorSigma[1, n+2]==2 DivisorSigma[1, n], Print[n]], {n, 2, 10^7}] (* or *) Select[Range[8000000], DivisorSigma[1, # + 2] == 2 DivisorSigma[1, #]&](* _Vincenzo Librandi_, Apr 04 2013 *)
%Y Cf. A000203, A002961, A175874, A175875.
%K nonn
%O 1,1
%A _Zak Seidov_, Oct 06 2010