A094468 Numbers k such that sum of 9th powers of divisors of k is divisible by the square of Euler-phi of k.

1, 2, 3, 6, 14, 42, 3810, 26670, 34162, 41256, 48546, 87096, 102486, 131934, 210482, 288792, 315723, 318990, 430122, 529848, 609672, 631446, 979830, 1023366, 1203960, 1473374, 1683126, 1920699, 2210061, 2241934, 2506086, 2549610

Offset: 1

Author

Labos Elemer, May 19 2004

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..420

Crossrefs

Cf. A015763, A000010, A091285, A013957.

Programs

Mathematica

Select[Range[2600000],Divisible[Total[Divisors[#]^9],(EulerPhi[#])^2]&]  (* Harvey P. Dale, Mar 04 2011 *)

PARI

for(n=1,10000000,if(Mod(sigma(n,9),eulerphi(n)^2)==0,print1(n,","))) \\ C. Ronaldo

Formula

A013957(k)/A000010(k)^2 is an integer.

Extensions

More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 18 2005