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A015847 Numbers k such that phi(k + 4) | sigma(k) for k not congruent to 0 (mod 3). 1
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified December 2 02:12 EST 2021. Contains 349435 sequences. (Running on oeis4.)