A015844 Numbers k such that phi(k) | sigma(k + 6).

1, 2, 4, 5, 6, 8, 9, 14, 15, 18, 24, 36, 45, 50, 56, 60, 72, 86, 98, 114, 148, 180, 204, 260, 264, 304, 315, 324, 370, 372, 420, 429, 434, 450, 456, 504, 546, 555, 602, 609, 610, 615, 684, 738, 746, 760, 786, 792, 868, 960, 982, 988, 1122, 1140, 1270, 1314

Offset: 1

Author

Robert G. Wilson v

Keywords

• nonn

Links

• Ivan Neretin, Table of n, a(n) for n = 1..1000

Programs

Mathematica

Select[Range[3000], Divisible[DivisorSigma[1, 6 + #], EulerPhi[#]] &]  (* David Nacin, Mar 03 2012 *)

PARI

is(n)=!(sigma(n+6)%eulerphi(n)) \\ Charles R Greathouse IV, Sep 25 2012

Extensions

a(1) = 1 inserted by Ivan Neretin, Feb 05 2017