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A015833 Numbers k such that phi(k + 13) | sigma(k). 1

%I #23 Aug 31 2018 02:53:38

%S 5,7,15,21,23,35,47,71,77,87,132,155,191,263,295,297,310,357,359,428,

%T 431,437,479,503,527,595,638,660,719,759,790,837,839,863,983,1002,

%U 1105,1151,1155,1223,1269,1336,1376,1463,1495,1511,1512,1559,1615,1817,1871

%N Numbers k such that phi(k + 13) | sigma(k).

%H Vincenzo Librandi, <a href="/A015833/b015833.txt">Table of n, a(n) for n = 1..2000</a>

%t Select[Range[3000], Divisible[DivisorSigma[1, #], EulerPhi[13 + #]] &] (* _David Nacin_, Mar 03 2012 *)

%o (PARI) is(n)=sigma(n)%(eulerphi(n)+13)==0 \\ _Charles R Greathouse IV_, Sep 25 2012

%K nonn

%O 1,1

%A _Robert G. Wilson v_

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Last modified May 20 11:25 EDT 2024. Contains 372712 sequences. (Running on oeis4.)