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

1,2

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

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 *)

Prog

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

Crossrefs

Cf. A068976.

Sequence in context: A005719 A143126 A118417 * A013194 A212874 A074447

Adjacent sequences: A069141 A069142 A069143 * A069145 A069146 A069147

Keyword

easy,nonn

Author

Benoit Cloitre, Apr 08 2002

Status

approved