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.
%I A046839 #30 Mar 17 2025 02:42:03 %S A046839 1,3,5,6,7,11,13,14,15,17,19,20,21,22,23,27,29,30,31,33,35,37,38,39, %T A046839 41,42,43,44,45,46,47,49,51,53,54,55,56,57,59,60,61,62,64,65,66,67,68, %U A046839 69,70,71,73,77,78,79,83,85,86,87,89,91,92,93,94,95,96,97,99,101,102,103 %N A046839 Numbers k such that the number of divisors of k divides the sum of cubes of divisors of k. %C A046839 The first 42 terms agree with A003601 but a(43) = 64 is not a term in A003601. %H A046839 Amiram Eldar, <a href="/A046839/b046839.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from T. D. Noe) %e A046839 64 is a term since it has 7 divisors, and sigma_3(64) = 299593 = 7 * 42799 is divisble by 7. %t A046839 Select[Range[103], Divisible[DivisorSigma[3, #], DivisorSigma[0, #]] &] (* _Jayanta Basu_, Jun 29 2013 *) %o A046839 (Magma) [n: n in [1..110] | IsZero(DivisorSigma(3, n) mod NumberOfDivisors(n))]; // _Bruno Berselli_, Apr 11 2013 %o A046839 (PARI) isok(n) = sigma(n, 3) % numdiv(n) == 0; \\ _Michel Marcus_, May 13 2018 %Y A046839 Cf. A000005, A001158. %Y A046839 Cf. A003601, A020486, A046840. %K A046839 nonn %O A046839 1,2 %A A046839 _Labos Elemer_