A015771 Numbers k such that phi(k) | sigma_13(k).

1, 2, 3, 6, 12, 14, 15, 30, 35, 42, 56, 70, 78, 105, 140, 168, 190, 210, 248, 264, 270, 357, 418, 420, 570, 594, 616, 630, 714, 744, 749, 812, 840, 910, 1045, 1240, 1254, 1485, 1498, 1672, 1848, 2090, 2214, 2247, 2376, 2436, 2568, 2580, 2730

Offset: 1

Author

Robert G. Wilson v

Keywords

• nonn

Comments

sigma_13(n) is the sum of the 13th powers of the divisors of n.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000010, A013961.

Cf. A020492, A015759, A015761, A015762, A015763, A015764, A015765, A015766, A015767, A015768, A015769, A015770, A015773, A015774, A094470.

Programs

Maple

with(numtheory); a := []: for n from 1 to 3000 do if sigma[13](n) mod phi(n) = 0 then a := [op(a), n]; fi; od: a;

Mathematica

Select[Range[3000], Divisible[DivisorSigma[13, #], EulerPhi[#]] &] (* Amiram Eldar, Nov 02 2019 *)

Formula

{n: A000010(n) | A013961(n)}. - R. J. Mathar, Sep 21 2017

Extensions

Offset corrected by Amiram Eldar, Nov 02 2019