A015812 - OEIS

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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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

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

MATHEMATICA

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

PROG

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

CROSSREFS

Sequence in context: A315229 A315230 A315231 * A358776 A315232 A175168

Adjacent sequences: A015809 A015810 A015811 * A015813 A015814 A015815

KEYWORD

nonn

AUTHOR

Robert G. Wilson v

STATUS

approved