%I #10 Sep 12 2015 13:59:59
%S 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 44,46,48,50,52,53,55,57,59,61,63,64,66,68
%N Longest checkmate in king and empress versus king endgame on an n X n chessboard.
%C An empress moves like a rook and a knight.
%H 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 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)
%F Conjecture: a(n) ~ 7*n/4.
%e 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 Cf. A137774, A218244, A225551, A225552, A225553, A225555, A225556, A225557, A227437.
%K nonn
%O 3,1
%A _Vaclav Kotesovec_, May 10 2013