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A069144 Numbers k such that A068976(k) divides k. 1
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified November 30 20:17 EST 2021. Contains 349425 sequences. (Running on oeis4.)