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A056097 Numbers n such that phi(n) + 1 | sigma(n). 3

%I

%S 6,8,30,36,44,156,696,944,2800,2928,3600,6660,16064,195456,260864,

%T 784128,4189184,12573696,201289728,17179541504,274876596224,

%U 824631361536

%N Numbers n such that phi(n) + 1 | sigma(n).

%C Contains 2^k(2^(k+2)-5) where 2^(k+2)-5 is prime; contains 2^k*3*(2^(k+2)-3) where 2^(k+2)-3 is prime; complete up to 5000000000. - _David W. Wilson_, May 16 2001

%C a(23) > 10^12. - _Donovan Johnson_, Feb 29 2012

%t Do[If[Mod[DivisorSigma[1, n], EulerPhi[n]+1]==0, Print[n]], {n, 1, 10^7}]

%K nonn

%O 1,1

%A _Robert G. Wilson v_, Jul 27 2000

%E a(20)-a(22) from _Donovan Johnson_, Feb 29 2012

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Last modified August 7 21:27 EDT 2022. Contains 355994 sequences. (Running on oeis4.)