A069144 Numbers k such that A068976(k) divides k.

1, 2, 12, 40, 120, 208, 280, 396, 440, 520, 624, 672, 680, 760, 920, 1040, 1160, 1240, 1456, 1480, 1640, 1720, 1880, 2120, 2288, 2360, 2440, 2680, 2840, 2920, 3120, 3160, 3320, 3360, 3392, 3536, 3560, 3880, 3952, 3960, 4040, 4120, 4280, 4360, 4368, 4520

Offset: 1

Author

Benoit Cloitre, Apr 08 2002

Keywords

• easy
• nonn

Comments

For n > 4 A068976(a(n)) >= 40 and almost all terms k in the sequence are such that A068976(k) = 40.

Links

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

Crossrefs

Cf. A068976.

Programs

Mathematica

f[p_, e_] := If[OddQ[e], 2*(p^(e + 1) - 1)/(p^2 - 1), (p^(e + 2) + p^e - 2)/(p^2 - 1)]; s[1] = 1; s[n_] := Times @@ (f @@@ FactorInteger[n]); Select[Range[5000], Divisible[#, s[#]] &] (* Amiram Eldar, Sep 03 2020 *)

PARI

for(n=1,10000,if(n%sumdiv(n,d,d/core(d))==0,print1(n,",")))