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A068078 Numbers n such that (sigma(n)+sigma(n+1))/n is an integer. 4

%I

%S 1,10,34,136,169,2402,5329,21004,38184,41164,54722,458010,776112,

%T 1060802,5026562,10800112,11108164,14366402,65676408,87026656,

%U 102944992,387999360,1488668112,4414086384,10499710072,28645019964

%N Numbers n such that (sigma(n)+sigma(n+1))/n is an integer.

%C The quotient (sigma(a(n)))+sigma(a(n)+1))/a(n) is equal to 3 or 4 for n <= 33 and equal to 5 for a(34) = 1170035543040. - _Giovanni Resta_, Apr 04 2014

%H Giovanni Resta, <a href="/A068078/b068078.txt">Table of n, a(n) for n = 1..34</a>

%t For[n=1, True, n++, If[Mod[DivisorSigma[1, n]+DivisorSigma[1, n+1], n]==0, Print[n]]]

%Y Cf. A067806, A068077.

%K nonn

%O 1,2

%A _Dean Hickerson_, Feb 16 2002

%E a(22)-a(26) from _Donovan Johnson_, Jan 31 2009

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Last modified September 17 12:40 EDT 2021. Contains 347477 sequences. (Running on oeis4.)