A015812 Composite numbers k such that phi(k) + 2 | sigma(k).

6, 10, 14, 22, 24, 26, 27, 28, 34, 38, 40, 45, 46, 54, 58, 62, 74, 82, 86, 90, 94, 106, 118, 122, 132, 134, 142, 146, 158, 166, 178, 184, 194, 202, 206, 214, 218, 226, 254, 260, 262, 274, 278, 298, 302, 314, 326, 334, 346, 358, 362, 374, 382, 386, 394, 398

Offset: 1

Author

Robert G. Wilson v

Keywords

• nonn

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..5000

Programs

Mathematica

Select[Range[1000], Divisible[DivisorSigma[1, #], EulerPhi[#] + 2] && ! PrimeQ[#] &] (* David Nacin, Mar 01 2012 *)

PARI

is(n)=!isprime(n) && sigma(n)%(eulerphi(n)+2)==0 \\ Charles R Greathouse IV, Sep 25 2012