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%I #15 May 13 2013 14:12:39
%S 6,34,50,236,262,386,898,8362,26938,46594,80876,5244548,5462384,
%T 17062316,323987588,1162300834,1381439876
%N Numbers n such that sigma(n) + sigma(n-1) = 3n, where sigma(n) = sum of divisors of n (A000203).
%C 34 is the only number < 10^10 such that sigma(n) + sigma(n+1) = sigma(n) + sigma(n-1) = 3n (34 is a term of A067806).
%C a(16) > 5*10^8. - _Giovanni Resta_, May 13 2013
%C a(18) > 10^10. - _Donovan Johnson_, May 13 2013
%t For[n=1, True, n++, If[DivisorSigma[1, n]+DivisorSigma[1, n-1]==3n, Print[n]]]
%o (PARI) is(n)=sigma(n)+sigma(n-1)==3*n \\ _Charles R Greathouse IV_, May 13 2013
%Y Cf. A067806 (numbers n such that sigma(n) + sigma(n+1) = 3n), A000203.
%K nonn
%O 1,1
%A _Jaroslav Krizek_, May 13 2013
%E a(12)-a(15) from _Giovanni Resta_, May 13 2013
%E a(16)-a(17) from _Donovan Johnson_, May 13 2013
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