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 A374013 #22 Jul 20 2024 14:46:13 %S A374013 0,1,0,1,1,1,2,2,2,2,3,3,3,3,3,4,4 %N A374013 n-queens completion threshold. The maximum number such that placing a(n) or fewer mutually non-attacking queens on an n X n chessboard is always completeable to a full n-queen configuration. %C A374013 For n large enough, n/60 <= a(n) <= 0.241*n [Glock et al.]. %H A374013 I. P. Gent, C. A. Jefferson, and P. W. Nightingale, <a href="https://doi.org/10.1613/jair.5512">Complexity of n-Queens Completion</a>, Journal of Artificial Intelligence Research, 59, 815-848. %H A374013 S. Glock, D. M. Correia, and B. Sudakov, <a href="https://doi.org/10.1007/s40687-022-00335-1">The n-queens completion problem</a>, Res Math Sci, 9 (2022), 41. %H A374013 Hugo M. Nielsen, <a href="https://gist.github.com/dragonoverlord3000/8c9757bd5aeb16d6aa3af6f4a1397810">C implementation</a> %e A374013 There are 2 solutions to the 4-queens problem: %e A374013 . Q . . %e A374013 . . . Q %e A374013 Q . . . %e A374013 . . Q . %e A374013 and %e A374013 . . Q . %e A374013 Q . . . %e A374013 . . . Q %e A374013 . Q . . %e A374013 Neither of these has a queen in the upper left corner, so placing a queen here will definitely make the configuration non-completable, while placing no queens is completable, see the two examples. %o A374013 (C) \\ see github link %Y A374013 Cf. A000170. %K A374013 nonn,more %O A374013 4,7 %A A374013 _Hugo M. Nielsen_, Jun 25 2024