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 A272719 #14 May 28 2021 18:56:41 %S A272719 2,5,8,12,17 %N A272719 Maximal number of steps in a nontouching path on an n X n grid such that each step has a different length. %C A272719 a(7) >= 22, see illustration in Links. %H A272719 Giovanni Resta, <a href="/A272719/a272719.png">Illustration of a(2)-a(6) and a(7) >= 22</a> %e A272719 An example for a(6)=17: %e A272719 ---------------- %e A272719 . 2 5 7 9 15 %e A272719 3 1 . . 11 17 %e A272719 . . . . . . %e A272719 . 6 . 12 . . %e A272719 4 10 . . . . %e A272719 8 13 . 14 16 18 %Y A272719 Cf. A226595. %K A272719 nonn,hard,more %O A272719 2,1 %A A272719 _Giovanni Resta_, May 05 2016