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 A225554 #12 Dec 01 2024 04:53:07 %S A225554 3,5,7,8,10,11,13,14,16,18,19,21,23,25,26,28,30,32,34,35,37,39,41,43, %T A225554 44,46,48,50,52,53,55,57,59,61,63,64,66,68 %N A225554 Longest checkmate in king and empress versus king endgame on an n X n chessboard. %C A225554 An empress moves like a rook and a knight. %H A225554 V. Kotesovec, <a href="http://problem64.beda.cz/silo/kotesovec_icga_2001.pdf">King and Two Generalised Knights against King</a>, ICGA Journal, Vol. 24, No. 2, pp. 105-107 (2001) %H A225554 V. Kotesovec, <a href="https://oeis.org/wiki/User:Vaclav_Kotesovec">Fairy chess endings on an n x n chessboard</a>, Electronic edition of chess booklets by Vaclav Kotesovec, vol. 8, p.363 (2013), p. 543 (second edition, 2017). %F A225554 Conjecture: a(n) ~ 7*n/4. %e A225554 Longest win on an 8x8 chessboard: Ka1 EMb1 - Kd4, 1.Ka1-a2 Kd4-e5 2.Ka2-b3 Ke5-f4 3.Kb3-c3 Kf4-e5 4.EMb1-b6! Ke5-f4 5.Kc3-d4 Kf4-g5 6.Kd4-e4 Kg5-g4! 7.EMb6-e6 Kg4-g3! 8.EMe6-f4! Kg3-h2! 9.Ke4-f3! Kh2-g1! 10.Kf3-g3 Kg1-h1! 11.EMf4-f1#, therefore a(8) = 11. %Y A225554 Cf. A137774, A218244, A225551, A225552, A225553, A225555, A225556, A225557, A227437. %K A225554 nonn %O A225554 3,1 %A A225554 _Vaclav Kotesovec_, May 10 2013