%I A048987
%S A048987 1,20,400,8902,197281,4865609,119060324,3195901860,84998978956,
%T A048987 2439530234167,69352859712417,2097651003696806
%N A048987 Number of possible chess games at the end of the n-th plie.
%C A048987 Does not include games which end in fewer than n plies.
%C A048987 According to the laws of chess, the "50 move rule" and "draw by repetition 
               of position" require an appeal by one of the players. So infinite 
               games are possible.
%H A048987 A. Bertilsson, <a href="http://www.albert.nu/programs/dperft/main.htm">
               Distributed Perft Project</a> [also found a(11)]
%H A048987 F. Labelle, <a href="http://www.cs.berkeley.edu/~flab/chess/statistics-games.html">
               Statistics on chess games</a>
%H A048987 T. Sillke, <a href="http://www.mathematik.uni-bielefeld.de/~sillke/SEQUENCES/
               series014">number of legal chess positions</a>
%H A048987 R. P. Stanley, <a href="http://www-math.mit.edu/~rstan/transparencies/
               iap.pdf">Extremal [Chess] Problems</a>
%H A048987 <a href="Sindx_Ch.html#chess">Index entries for sequences related to 
               number of chess games</a>
%Y A048987 Cf. A006494, A079485, A083276, A019319.
%Y A048987 Sequence in context: A057745 A009964 A007577 this_sequence A006494 A007545 
               A055476
%Y A048987 Adjacent sequences: A048984 A048985 A048986 this_sequence A048988 A048989 
               A048990
%K A048987 nonn,nice,hard
%O A048987 0,2
%A A048987 Steven J. Edwards (sje(AT)mv.mv.com)
%E A048987 a(10) from Richard Bean (rwb(AT)eskimo.com), Jun 02 2003
%E A048987 a(11) from Francois Labelle (flab(AT)cs.berkeley.edu), Jul 25 2004, who 
               thanks Joost de Heer for providing computer time.