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 A320421 #7 Jan 08 2019 19:09:03 %S A320421 0,1,3,14,70,372,2058,11752,68706,409130,2472646,15127620,93504944, %T A320421 583032968,3662883960,23163461280,147329432094,941880843108, %U A320421 6049001532148,39007700026460,252477751201074,1639657957610596,10680997864879592,69772819359471480,456959583009324200 %N A320421 Number of closed self-avoiding paths on square lattice with 2*n steps, A010566(n)/8. %C A320421 Rotations and reflections of the path are counted only once, but see A266549 for further elimination of path isomorphisms. %D A320421 See A010566. %Y A320421 Cf. A002931, A010566, A266549. %K A320421 nonn,walk %O A320421 1,3 %A A320421 _Hugo Pfoertner_, Jan 08 2019