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 A045746 #17 Jun 20 2021 02:29:00 %S A045746 1,2,5,8,12,22,36,45,54,56,87,95,98,104,116,152,160,200,212,258,328, %T A045746 342,356,393,427,441,473,492,531,572,582,588,660,668,672,726,740,800, %U A045746 843,852,858,879,908,909,910,940,962,992 %N A045746 Numbers whose sum of divisors is a triangular number. %H A045746 Charles R Greathouse IV, <a href="/A045746/b045746.txt">Table of n, a(n) for n = 1..10000</a> %e A045746 sigma(8)=15 is a triangular number. %t A045746 Select[Range[1000],IntegerQ[(Sqrt[1+8DivisorSigma[1,#]]-1)/2]&] (* _Harvey P. Dale_, Jul 14 2011 *) %o A045746 (PARI) is(n)=ispolygonal(sigma(n),3) \\ _Charles R Greathouse IV_, Nov 10 2014 %Y A045746 Cf. A000203, A000217. %K A045746 nonn %O A045746 1,2 %A A045746 _Felice Russo_