cp's OEIS Frontend

A046841 Numbers whose sum of divisors divides their sum of cubes of divisors.

%I A046841 #39 Jan 16 2025 19:37:07
%S A046841 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 A046841 31,33,34,35,37,38,39,40,41,42,43,46,47,48,51,53,54,55,56,57,58,59,60,
%U A046841 61,62,64,65,66,67,68,69,70,71,72,73,74,76,77,78,79,80,81,82,83,84,85
%N A046841 Numbers whose sum of divisors divides their sum of cubes of divisors.
%C A046841 A005117 (squarefree numbers) is a subsequence. - _Ivan Neretin_, Dec 20 2017
%H A046841 Amiram Eldar, <a href="/A046841/b046841.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from Paolo P. Lava)
%e A046841 2 is a term because 1 + 8 = 9 is divisible by 1 + 2 = 3.
%e A046841 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 A046841 with(numtheory):
%p A046841 for n to 100 do
%p A046841  if (type(sigma[3](n)/sigma[1](n), integer)) then print(n) end if;
%p A046841 end do; # _Peter Bala_, Jan 12 2025
%t A046841 Select[Range@ 85, Divisible[DivisorSigma[3, #], DivisorSigma[1, #]] &] (* _Michael De Vlieger_, Aug 01 2017 *)
%o A046841 (PARI) isA046841(n)=sigma(n,3)%sigma(n,1)==0 \\ _Michael B. Porter_, Apr 07 2010
%Y A046841 Cf. A000203, A001158, A005117.
%Y A046841 Cf. A003601, A020486.
%K A046841 nonn
%O A046841 1,2
%A A046841 _Labos Elemer_