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A195864 Numbers n such that sigma(n) + tau(n) is a perfect number (A000396). 0

%I #21 Aug 03 2014 14:01:34

%S 3,14,15,168,326,5414,33357341,4324809536

%N Numbers n such that sigma(n) + tau(n) is a perfect number (A000396).

%C A002093(848) < a(9) <= 1155321467378283328. - Donovan Johnson, Nov 03 2011

%t perfect = {6, 28, 496, 8128, 33550336, 8589869056, 137438691328}; Select[Range[10000], MemberQ[perfect, DivisorSigma[0, #] + DivisorSigma[1, #]] &] (* _T. D. Noe_, Nov 03 2011 *)

%Y Cf. A007503 (sigma(n) + tau(n)).

%K nonn

%O 1,1

%A _Jeff Kruse_, Oct 26 2011

%E a(8) from _Donovan Johnson_, Nov 03 2011

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Last modified March 18 22:56 EDT 2024. Contains 370952 sequences. (Running on oeis4.)