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A015853

Numbers k such that phi(k) | sigma(k + 9).

1, 2, 3, 4, 5, 6, 10, 12, 13, 14, 21, 24, 26, 30, 31, 37, 42, 45, 48, 50, 57, 60, 68, 76, 78, 96, 105, 111, 133, 156, 168, 175, 181, 196, 200, 215, 273, 286, 288, 290, 310, 320, 336, 350, 361, 369, 381, 399, 406, 420, 450, 465, 543, 585, 600, 612, 656, 740

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OFFSET

1,2

LINKS

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

MATHEMATICA

Select[Range[1000], Divisible[DivisorSigma[1, #+9], EulerPhi[#]] &] (* Amiram Eldar, Dec 13 2018 *)

PROG

(PARI) is(n)=!(sigma(n+9)%eulerphi(n)) \\ Charles R Greathouse IV, Sep 25 2012

(Magma) [n: n in [1..900] | DivisorSigma(1, n+9) mod EulerPhi(n) eq 0]; // G. C. Greubel, Dec 13 2018

CROSSREFS