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 A323700 #12 Apr 12 2019 13:50:14 %S A323700 1,8,56,406,2572,16596,102654,642441,3914084 %N A323700 Number of rooted uncrossed knight's walks on an infinite chessboard trapped after n moves with first move specified. %C A323700 Trapping occurs if the walk cannot be continued without reusing an already visited field or creating an intersection of the path segments formed by straight lines connecting consecutively visited fields. %C A323700 The shortest self-trapped walk has 4 moves, i.e., a(n)=0 for n < 4. %e A323700 a(4) = 1 because there is only one trapped walk of 4 moves, written in algebraic chess notation: (N) b1 d2 b3 a1 c2. %e A323700 For longer walks see link to illustrations in A323699. %Y A323700 Cf. A003192, A323131, A323559, A323560, A323699. %K A323700 nonn,walk,more,hard %O A323700 4,2 %A A323700 _Hugo Pfoertner_, Jan 24 2019