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 A368061 #17 Dec 19 2023 16:50:30 %S A368061 0,0,0,0,0,0,1,0,5,0,18,0,50,0,652,0,4260,0,25134,0,238098,0,2492304, %T A368061 0,25389294 %N A368061 The number of ways to place one pawn and n+1 nonattacking queens on an n X n chessboard, unchanged by 180-degree rotation. %C A368061 n must be odd, and the pawn must be in the center. %F A368061 A103330(n) = 8*A103331(n) - 4*a(n). %e A368061 For n=7 the a(7)=1 solution is %e A368061 . . Q . . . . %e A368061 . . . . . Q . %e A368061 . . . Q . . . %e A368061 Q . . P . . Q %e A368061 . . . Q . . . %e A368061 . Q . . . . . %e A368061 . . . . Q . . %Y A368061 A103330 counts all solutions; A103331 counts them with symmetry removed. %K A368061 nonn,more %O A368061 1,9 %A A368061 _Don Knuth_, Dec 10 2023