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 A327131 #18 Apr 05 2020 03:15:16 %S A327131 1,20,6,9,4,8,5,10,13,2,14,7,11,22,3,15,12,23,26,29,16,19,34,54,17,31, %T A327131 50,47,24,21,18,32,35,55,30,27,45,68,25,42,39,36,33,53,78,48,51,76, %U A327131 106,49,73,28,46,43,40,37,58,84,87,60,63,41,69,72,101,67,44 %N A327131 Cells visited by knight moves on a spirally numbered infinite hexagonal board, moving to the lowest unvisited cell at each step. %C A327131 The infinite hexagonal board is numbered spirally as: %C A327131 . %C A327131 17--18--19... %C A327131 / %C A327131 16 6---7---8 %C A327131 / / \ %C A327131 15 5 1---2 9 %C A327131 \ \ / / %C A327131 14 4---3 10 %C A327131 \ / %C A327131 13--12--11 %C A327131 . %C A327131 In Glinski's hexagonal chess, a knight (N) can move to these (o) cells: %C A327131 . %C A327131 . . . . . %C A327131 . . o o . . %C A327131 . o . . . o . %C A327131 . o . . . . o . %C A327131 . . . . N . . . . %C A327131 . o . . . . o . %C A327131 . o . . . o . %C A327131 . . o o . . %C A327131 . . . . . %C A327131 . %C A327131 This sequence is finite and ends at a(83966) = 72085 when the knight is "trapped". %H A327131 Sangeet Paul, <a href="/A327131/b327131.txt">Table of n, a(n) for n = 1..83966</a> %H A327131 Scott R. Shannon, <a href="/A327131/a327131.png">Image showing the 83965 steps of the knight's path</a>. The green central dot is the starting square and the red dot, located on the edge at the 7:30 clock position, the final square. Blue dots show the twelve occupied squares surrounding the final square. The lowest unvisited square, 71301, is the yellow dot on the edge at the 9:00 clock position. %H A327131 Chess variants, <a href="https://www.chessvariants.com/hexagonal.dir/hexagonal.html">Glinski's Hexagonal Chess</a> %H A327131 Wikipedia, <a href="https://en.wikipedia.org/wiki/Hexagonal_chess#Gli%C5%84ski's_hexagonal_chess">Hexagonal chess - Gliński's hexagonal chess</a> %Y A327131 Cf. A316667, A327132. %K A327131 nonn,fini,full %O A327131 1,2 %A A327131 _Sangeet Paul_, Aug 22 2019