A015847 Numbers k such that phi(k + 4) | sigma(k) for k not congruent to 0 (mod 3).

5, 10, 14, 22, 34, 35, 38, 58, 70, 82, 95, 110, 118, 140, 142, 143, 191, 202, 214, 224, 230, 274, 298, 308, 358, 374, 376, 382, 394, 454, 478, 538, 562, 590, 598, 616, 620, 622, 623, 694, 728, 838, 862, 920, 922, 1012, 1042, 1121, 1138, 1198

Offset

1,1

Links

G. C. Greubel, Table of n, a(n) for n = 1..1000

Mathematica

Select[Range[1000], Mod[#, 3] > 0 && Divisible[DivisorSigma[1, #], EulerPhi[#+4]] &] (* Amiram Eldar, Dec 13 2018 *)

Prog

(PARI) is(n)=n%3 && !(sigma(n)%eulerphi(n+4)) \\ Charles R Greathouse IV, Sep 25 2012
(Magma) [n: n in [1..1000] | n mod 3 ne 0 and DivisorSigma(1, n) mod EulerPhi(n+4) eq 0]; // G. C. Greubel, Dec 13 2018

Crossrefs

Subsequence of A015820.

Sequence in context: A313664 A023494 A313665 * A224692 A020885 A258151

Adjacent sequences: A015844 A015845 A015846 * A015848 A015849 A015850

Keyword

nonn

Author

Robert G. Wilson v

Extensions

Title and PARI program corrected by Sean A. Irvine, Dec 13 2018

Status

approved