login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A069144 Numbers k such that A068976(k) divides k. 1

%I

%S 1,2,12,40,120,208,280,396,440,520,624,672,680,760,920,1040,1160,1240,

%T 1456,1480,1640,1720,1880,2120,2288,2360,2440,2680,2840,2920,3120,

%U 3160,3320,3360,3392,3536,3560,3880,3952,3960,4040,4120,4280,4360,4368,4520

%N Numbers k such that A068976(k) divides k.

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

%H Amiram Eldar, <a href="/A069144/b069144.txt">Table of n, a(n) for n = 1..10000</a>

%t 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 *)

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

%Y Cf. A068976.

%K easy,nonn

%O 1,2

%A _Benoit Cloitre_, Apr 08 2002

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified January 22 02:46 EST 2022. Contains 350481 sequences. (Running on oeis4.)