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Numbers k such that phi(k) | sigma_18(k).
11

%I #15 Mar 07 2020 06:51:29

%S 1,2,3,6,22,33,66,262,750,786,2182,6546,8646,56946,72006,162066,

%T 222386,626406,667158,737286,857526,1223123,1489686,1782726,2446246,

%U 2939046,3669369,4388406,4780947,6804006,7338738,9561894,10761126,12157926

%N Numbers k such that phi(k) | sigma_18(k).

%C A015759 seems to be a true subsequence here.

%C sigma_18(n) is the sum of the 18th powers of the divisors of n (A013966). Conjecture: analogous sequences with any 4j+2 exponent instead of 18, includes all terms of A015759 [with exponent=2].

%H Amiram Eldar, <a href="/A094470/b094470.txt">Table of n, a(n) for n = 1..130</a>

%t Select[Range[10^6], Divisible[DivisorSigma[18, #], EulerPhi[#]] &] (* _Amiram Eldar_, Mar 07 2020 *)

%o (PARI) isok(k) = (sigma(k, 18) % eulerphi(k)) == 0; \\ _Michel Marcus_, Mar 07 2020

%Y Cf. A000010, A013966, A015759.

%K nonn

%O 1,2

%A _Labos Elemer_, May 25 2004