cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A303993 Numbers whose sum of divisors is the cube of one of their divisors.

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%I A303993 #13 May 08 2018 02:42:20
%S A303993 1,102,8148,63720,66120,71880,196896,446040,452760,462840,471960,
%T A303993 503160,517320,544920,549240,554280,559320,575880,756400,1458912,
%U A303993 1499232,1579872,1634040,1659960,1748520,5294800,9740640,10103520,11103456,11438280,11583264,11619720,11915640
%N A303993 Numbers whose sum of divisors is the cube of one of their divisors.
%C A303993 Subset of A020477.
%e A303993 Divisors of 102 are 1, 2, 3, 6, 17, 34, 51, 102 and their sum is 216 = 6^3.
%p A303993 with(numtheory): P:=proc(q) local a,k,n;
%p A303993 for n from 1 to q do a:=sort([op(divisors(n))]);
%p A303993 for k from 1 to nops(a) do if sigma(n)=a[k]^3 then print(n); break; fi; od; od; end: P(10^9);
%t A303993 Select[Range[10^6], Mod[#, DivisorSigma[1, #]^(1/3)] == 0 &] (* _Michael De Vlieger_, May 06 2018 *)
%o A303993 (PARI) isok(n) = (n==1) || (ispower(s=sigma(n), 3) && !(n % sqrtnint(s, 3))); \\ _Michel Marcus_, May 05 2018
%Y A303993 Cf. A000203, A020477, A303123, A303994, A303995, A303996.
%K A303993 nonn,easy
%O A303993 1,2
%A A303993 _Paolo P. Lava_, May 04 2018