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 A253620 #15 Jan 23 2018 07:08:03 %S A253620 0,3,6,10,14,19,25,30,36 %N A253620 Maximum number of segments in nonintersecting increasing path on n X n hexagonal (isogonal) grid. %C A253620 The path cannot intersect itself, not even on single points. "Increasing" means that the (Euclidean) length of each segment must be strictly greater than that of the previous one. %C A253620 The analogous sequence for a triangular (isogonal) grid seems to satisfy a(n) = 2n+1, with 2^(n-2) such paths up to isomorphism. %H A253620 Tim Cieplowski, <a href="/A253620/a253620.png">Illustration of first few terms</a> %H A253620 Gordon Hamilton, <a href="https://www.youtube.com/watch?v=ZNmstUbD-pA">$1,000,000 Unsolved Problem for Grade 8</a> (2011) %e A253620 An example for a(4) = 10 %e A253620 . . . . %e A253620 09 . . . . %e A253620 01 . . . . . %e A253620 00 07 . . . . 10 %e A253620 02 05 . . . 08 %e A253620 . . . . 06 %e A253620 03 . . 04 %Y A253620 Cf. A226595. %K A253620 hard,more,nonn %O A253620 1,2 %A A253620 _Tim Cieplowski_, Jan 06 2015