A015858 Numbers k such that phi(k) | sigma(k + 11).

1, 2, 3, 4, 6, 8, 9, 10, 12, 13, 16, 18, 19, 20, 24, 35, 36, 45, 49, 51, 74, 77, 79, 84, 91, 104, 108, 113, 124, 129, 130, 144, 148, 180, 198, 219, 224, 279, 286, 308, 380, 407, 434, 435, 459, 490, 584, 609, 610, 616, 624, 627, 628, 640, 644, 679, 779

Offset

1,2

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Mathematica

Select[Range[800], Divisible[DivisorSigma[1, #+11], EulerPhi[#]]&] (* Harvey P. Dale, Aug 01 2016 *)

Prog

(PARI) is(n)=!(sigma(n+11)%eulerphi(n)) \\ Charles R Greathouse IV, Sep 25 2012
(Magma) [n: n in [1..900] | DivisorSigma(1, n+11) mod EulerPhi(n) eq 0]; // G. C. Greubel, Dec 13 2018

Crossrefs

Cf. A015834 (m=1), A015837 (m=2), A015840 (m=3), A015841 (m=4), A015843 (m=5), A015844 (m=6), A015845 (m=7), A015851 (m=8), A015853 (m=9), A015856 (m=10), this sequence (m=11), A015859 (m=12), A015860 (m=13).

Sequence in context: A026431 A026433 A354148 * A321473 A125292 A101513

Adjacent sequences: A015855 A015856 A015857 * A015859 A015860 A015861

Keyword

nonn

Author

Robert G. Wilson v

Extensions

Missing a(1)=1 inserted by Sean A. Irvine, Dec 13 2018

Status

approved