A015812 - OEIS

%I #28 Aug 31 2018 02:54:11

%S 6,10,14,22,24,26,27,28,34,38,40,45,46,54,58,62,74,82,86,90,94,106,

%T 118,122,132,134,142,146,158,166,178,184,194,202,206,214,218,226,254,

%U 260,262,274,278,298,302,314,326,334,346,358,362,374,382,386,394,398

%N Composite numbers k such that phi(k) + 2 | sigma(k).

%H Vincenzo Librandi, <a href="/A015812/b015812.txt">Table of n, a(n) for n = 1..5000</a>

%t Select[Range[1000], Divisible[DivisorSigma[1, #], EulerPhi[#] + 2] && ! PrimeQ[#] &] (* _David Nacin_, Mar 01 2012 *)

%o (PARI) is(n)=!isprime(n) && sigma(n)%(eulerphi(n)+2)==0 \\ _Charles R Greathouse IV_, Sep 25 2012

%K nonn

%O 1,1

%A _Robert G. Wilson v_