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%I #13 Dec 15 2017 17:35:48
%S 121679,1043909,2350171,2918263,3396103,3566807,3688067,4019467,
%T 4562827,5963407,7300697,7485979,7853933,8103301,8364151,9237779,
%U 9514213,9638527,10531123,11094619,11384447,12721937,13576267,15331313
%N Numbers n such that sigma(phi(n))/sigma(n) is an integer >= 4.
%C Conjecture: all natural numbers 1,2,3,...,n will eventually occur among the integer values of sigma(phi(n))/sigma(n).
%H Harry J. Smith, <a href="/A066881/b066881.txt">Table of n, a(n) for n = 1..370</a>
%e a(1) = 121679 because sigma(phi(121679))/sigma(121679) = 4.
%p 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: # _R. J. Mathar_, Oct 01 2008
%o (PARI) { n=0; for (m=1, 10^10, if((e=sigma(eulerphi(m))) % (s=sigma(m)) == 0 && e/s >= 4, write("b066881.txt", n++, " ", m); if (n==1000, return)) ) } \\ _Harry J. Smith_, Apr 03 2010
%Y Cf. A066817.
%Y Cf. A067383, A067382. - _R. J. Mathar_, Oct 01 2008
%K nonn
%O 1,1
%A _Jason Earls_, Jan 22 2002
%E Terms a(16) etc. from _R. J. Mathar_, Oct 01 2008
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