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 A103331 #11 Dec 17 2023 03:15:58 %S A103331 0,0,0,0,0,2,3,16,52,286,1403,8214,54756,389833,2923757,22932960, %T A103331 184339572 %N A103331 Number of ways to place n+1 queens and a pawn on an n X n board so that no two queens attack each other (symmetric solutions count only once). %H A103331 R. D. Chatham, <a href="http://people.moreheadstate.edu/fs/d.chatham/n+kqueens.html">The N+k Queens Problem Page</a>. %H A103331 R. D. Chatham, G. H. Fricke and R. D. Skaggs, <a href="http://people.moreheadstate.edu/fs/d.chatham/queenssep.pdf">The Queens Separation Problem</a>, Utilitas Mathematica 69 (2006), 129-141. %H A103331 R. D. Chatham, M. Doyle, G. H. Fricke, J. Reitmann, R. D. Skaggs and M. Wolff, <a href="http://people.moreheadstate.edu/fs/d.chatham/QueensSep2.pdf">Indepe ndence and Domination Separation in Chessboard Graphs</a>, Journal of Combinatorial Mathematics and Combinatorial Computing, to appear. %e A103331 For n=6 the a(6)=2 solutions are %e A103331 . . Q . . . . . Q . . . %e A103331 Q . P . . Q Q . P . . Q %e A103331 . . . Q . . . . Q . . . %e A103331 . Q . . . . . . . . Q . %e A103331 . . . . Q . . Q . . . . %e A103331 . . Q . . . . . . Q . . %Y A103331 Cf. A103330, A002562, A368061. %K A103331 more,nonn %O A103331 1,6 %A A103331 R. Douglas Chatham (d.chatham(AT)moreheadstate.edu), Jan 31 2005 %E A103331 More terms from R. Douglas Chatham (d.chatham(AT)moreheadstate.edu), Feb 15 2005, Apr 20 2007