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 A101857 #5 Jul 27 2015 19:23:03 %S A101857 0,0,0,0,0,0,1,1,0,0,0,0,0,0,16,28,0,0,0,0,0,0,1190,2108,0,0,0,0,0,0 %N A101857 Number of possibly-self-intersecting walks that it is possible for an accelerating ant to produce with n steps (rotations & reflections not included). On step 1 the ant moves forward 1 unit, then turns left or right and proceeds 2 units, then turns left or right until at the end of its n-th step it arrives back at its starting place. %C A101857 Accelerating ant walks can only arrive back at the starting place if the number of moves is -1 or 0 mod(8). %e A101857 a(7) = 1 because of the following solution: %e A101857 655555XXX %e A101857 6XXXX4XXX %e A101857 6XXXX4XXX %e A101857 6XXXX4XXX %e A101857 6XXXX4333 %e A101857 6XXXXXXX2 %e A101857 777777712 %e A101857 where the ant starts at the "1" and moves right 1 space, up 2 spaces and so on... %Y A101857 Cf. A101856. %K A101857 nice,nonn %O A101857 1,15 %A A101857 _Gordon Hamilton_, Jan 27 2005