Search: id:A066881
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%I A066881
%S A066881 121679,1043909,2350171,2918263,3396103,3566807,3688067,4019467,4562827,
%T A066881 5963407,7300697,7485979,7853933,8103301,8364151,9237779,9514213,
%U A066881 9638527,10531123,11094619,11384447,12721937,13576267,15331313
%N A066881 Numbers n such that sigma(phi(n))/sigma(n) is an integer >= 4.
%C A066881 Conjecture: all natural numbers 1,2,3,..n will eventually occur among 
               the integer values of sigma(phi(n))/sigma(n).
%e A066881 a(1)=121679 because sigma(phi(121679))/sigma(121679) = 4.
%p A066881 for n from 1 do spn := numtheory[sigma](numtheory[phi](n)) ; sn := numtheory[sigma](n) 
               ; if spn mod sn = 0 then if spn/sn >= 4 then print(n,spn/sn) fi; 
               fi; od: [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 01 
               2008]
%Y A066881 Cf. A066817.
%Y A066881 Cf. A067383, A067382. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), 
               Oct 01 2008]
%Y A066881 Sequence in context: A068136 A135495 A067384 this_sequence A048903 A115545 
               A104973
%Y A066881 Adjacent sequences: A066878 A066879 A066880 this_sequence A066882 A066883 
               A066884
%K A066881 nonn
%O A066881 1,1
%A A066881 Jason Earls (zevi_35711(AT)yahoo.com), Jan 22 2002
%E A066881 Terms a(16) etc. from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 
               01 2008

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