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 A338520 #11 Nov 01 2020 04:33:51 %S A338520 1,6,12,28,30,56,72,117,120,132,180,182,306,360,380,496,552,672,702, %T A338520 775,792,840,870,992,1080,1092,1406,1440,1568,1584,1680,1722,1836, %U A338520 1892,2016,2160,2184,2256,2280,2793,2862,3276,3312,3510,3540,3600,3672,3696,3782,3960 %N A338520 Integers that can be expressed as a product d*sigma(d), where sigma is the sum of divisors function, in a single way. %C A338520 Integers m such that A327153(m) = 1. %H A338520 David A. Corneth, <a href="/A338520/b338520.txt">Table of n, a(n) for n = 1..10000</a> %o A338520 (PARI) f(n) = sumdiv(n, d, d*sigma(d)==n); \\ A327153 %o A338520 isok(n) = f(n)==1; %Y A338520 Cf. A000203, A064987, A327153, A337873. %Y A338520 Subsequence of A327165. %Y A338520 Subsequences: A000396 (perfect numbers), A036690 (p*(p+1)). %Y A338520 Cf. A338519 (similar for number of divisors). %K A338520 nonn %O A338520 1,2 %A A338520 _Michel Marcus_, Nov 01 2020