login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A046841 Sum of divisors divides sum of cubes of divisors. 3

%I

%S 1,2,3,5,6,7,8,10,11,12,13,14,15,16,17,19,20,21,22,23,24,26,27,29,30,

%T 31,33,34,35,37,38,39,40,41,42,43,46,47,48,51,53,54,55,56,57,58,59,60,

%U 61,62,64,65,66,67,68,69,70,71,72,73,74,76,77,78,79,80,81,82,83,84,85

%N Sum of divisors divides sum of cubes of divisors.

%C A005117 (squarefree numbers) is a subsequence. - _Ivan Neretin_, Dec 20 2017

%H Paolo P. Lava, <a href="/A046841/b046841.txt">Table of n, a(n) for n = 1..1000</a>

%e 2 is a term because 1+8 = 9 is divisible by 1+2 = 3.

%e x=208 is a term: The power sums of divisors for k=0,1,2,3 are as follows: 10,434,54970,10288838; and sigma(1,208)=434 divides sigma(3,208)=10288838=434*23707.

%p with(numtheory);

%p List046841:=proc(q) local a,b,k,n;

%p for n from 1 to q do

%p a:=divisors(n); b:=add(a[k]^3,k=1..nops(a));

%p if type(b/sigma(n),integer) then print(n); fi;

%p od; end:

%p List046841(10^6); # _Paolo P. Lava_, Apr 10 2013

%t Select[Range@ 85, Divisible[DivisorSigma[3, #], DivisorSigma[1, #]] &] (* _Michael De Vlieger_, Aug 01 2017 *)

%o (PARI) isA046841(n)=sigma(n,3)%sigma(n,1)==0 \\ _Michael B. Porter_, Apr 07 2010

%Y Cf. A000203, A001158.

%Y Cf. A003601, A020486.

%K nonn

%O 1,2

%A _Labos Elemer_

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 16 23:12 EDT 2018. Contains 316275 sequences. (Running on oeis4.)