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 A360777 #13 Feb 16 2025 08:34:04 %S A360777 9,160,143,2679,19933,115248,45,1995 %N A360777 a(n) is the index of the least n-gonal number that is the sum of two or more consecutive nonzero n-gonal numbers in more than one way, or -1 if no such number exists. %C A360777 a(10)>2000000, a(11)=24375, a(12)=133307113, a(13)=6715891, a(16)=189308, a(20)=9009. - _Sean A. Irvine_, Mar 24 2023 %H A360777 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PolygonalNumber.html">Polygonal Number</a> %Y A360777 Cf. A057145, A360762. %K A360777 nonn,more %O A360777 2,1 %A A360777 _Ilya Gutkovskiy_, Feb 20 2023