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 A226239 #40 Aug 03 2022 22:27:11 %S A226239 1,3,6,10,15,22,33,44,59,76,101,125,158 %N A226239 Minimum m such that there exists an n-row subtractive triangle with distinct integers in 1..m. %C A226239 In an n-row subtractive triangle, there are n-i+1 integers in the i-th row. The integers in the first row are arbitrary. From the next row, the integers are the absolute difference between adjacent integers in the previous row. %H A226239 Chyanog, <a href="http://bbs.emath.ac.cn/thread-4977-1-1.html">A Chinese web page where the problem was posed</a>. %H A226239 International Mathematical Olympiad, <a href="https://www.imo-official.org/problems.aspx">Problem 3 of IMO 2018</a>. %H A226239 Denis Cazor, <a href="/A226239/a226239.pdf">Algorithme en Français</a> %H A226239 Denis Cazor, <a href="/A226239/a226239_1.pdf">Algorithm in English</a> %e A226239 a(6)=22 because there is a 6-row subtractive triangle with distinct integers in [1..22] as follows: %e A226239 1: 6 20 22 3 21 13 %e A226239 2: 14 2 19 18 8 %e A226239 3: 12 17 1 10 %e A226239 4: 5 16 9 %e A226239 5: 11 7 %e A226239 6: 4 %e A226239 However, there is no such triangle with distinct integers in [1..21]. %Y A226239 Cf. A035312, A035313. %K A226239 nonn,hard,more %O A226239 1,2 %A A226239 _Yi Yang_, Jun 01 2013 %E A226239 a(12) from _Yi Yang_, Mar 04 2015 %E A226239 a(13) from _Denis Cazor_, Aug 01 2022