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 A015856 Numbers k such that phi(k) | sigma(k + 10). 5

%I

%S 1,2,3,4,5,7,12,13,14,20,28,29,32,36,44,45,52,53,56,60,66,77,84,86,

%T 104,105,108,110,123,130,144,172,221,228,238,270,287,312,342,366,380,

%U 385,396,441,468,558,584,585,588,644,672,750,754,760,854,864

%N Numbers k such that phi(k) | sigma(k + 10).

%H G. C. Greubel, <a href="/A015856/b015856.txt">Table of n, a(n) for n = 1..1000</a>

%t Select[Range[1000], Divisible[DivisorSigma[1,#+10], EulerPhi[#]] &] (* _Amiram Eldar_, Dec 13 2018 *)

%o (PARI) is(n)=!(sigma(n+10)%eulerphi(n)) \\ _Charles R Greathouse IV_, Sep 25 2012

%o (MAGMA) [n: n in [1..900] | DivisorSigma(1,n+10) mod EulerPhi(n) eq 0]; // _G. C. Greubel_, Dec 13 2018

%Y Cf. A015834 (m=1), A015837 (m=2), A015840 (m=3), A015841 (m=4), A015843 (m=5), A015844 (m=6), A015845 (m=7), A015851 (m=8), A015853 (m=9), this sequence (m=10), A015858 (m=11), A015859 (m=12), A015860 (m=13).

%K nonn

%O 1,2

%A _Robert G. Wilson v_

%E Missing a(1)=1 inserted by _Sean A. Irvine_, Dec 13 2018

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Last modified April 23 07:51 EDT 2019. Contains 322381 sequences. (Running on oeis4.)