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Numbers k such that phi(k + 7) | sigma(k) for k not congruent to 0 (mod 3).
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%I #17 Sep 08 2019 19:04:27

%S 11,14,23,35,59,71,77,107,110,119,131,140,158,161,167,179,203,239,251,

%T 253,280,287,290,304,311,329,347,359,371,383,413,419,430,431,467,491,

%U 497,581,599,623,647,665,713,728,749,770,827,836,887,893,971,1031,1043

%N Numbers k such that phi(k + 7) | sigma(k) for k not congruent to 0 (mod 3).

%t Select[Range[1, 5000], Divisible[DivisorSigma[1, #], EulerPhi[7 + #]] && ! Mod[#, 3] == 0 &] (* _David Nacin_, Mar 04 2012 *)

%o (PARI) is(n)=n%3 && sigma(n)%eulerphi(n+7)==0 \\ _Charles R Greathouse IV_, Sep 25 2012

%K nonn

%O 1,1

%A _Robert G. Wilson v_