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 A324273 #14 May 10 2019 16:51:03 %S A324273 1,4,7,2,5,12,17,8,13,6,3,10,15,26,19,32,25,14,9,18 %N A324273 Squares visited by a single pawn move for an even square and a double pawn move for an odd square on a diagonally numbered board and moving to the lowest available unvisited square of different parity at each step. %C A324273 The board is numbered as follows: %C A324273 1 2 4 7 11 16 . %C A324273 3 5 8 12 17 . %C A324273 6 9 13 18 . %C A324273 10 14 19 . %C A324273 15 20 . %C A324273 21 . %C A324273 . %e A324273 Square 1 is odd. Hence the next square should be the lowest even square a double move away from 1, which is square 4. Next, there is only a single option to move in a single move to an odd square, namely at square 7. Etc. %Y A324273 Cf. A316588, A324274, A324275. %K A324273 nonn,fini,full %O A324273 1,2 %A A324273 _Jan Koornstra_, Feb 20 2019