A089957 - OEIS

%I #26 Jan 08 2017 12:52:00

%S 1,20,400,1862,9825,53516,311642,2018993,12150635,69284509,382383387,

%T 1994236773

%N Number of chess positions that can be obtained in exactly one way in n plies.

%C Definition: position = position with castling and en passant information, diagram = position without castling and en passant information.

%C The positions are taken from the sets that are counted in A083276.

%H F. Labelle, <a href="http://www.cs.berkeley.edu/~flab/chess/statistics-positions.html">Statistics on chess positions</a>

%H P. Österlund, <a href="http://www.talkchess.com/forum/viewtopic.php?topic_view=threads&amp;p=508645&amp;t=41032">Computation of a(11)</a>.

%H <a href="/index/Ch#chess">Index entries for sequences related to number of chess games</a>

%Y Cf. A083276, A090051.

%K nonn,hard,more,fini

%O 0,2

%A _François Labelle_, Jan 12 2004

%E a(9) from _François Labelle_, Mar 09 2004

%E a(10) from _Arkadiusz Wesolowski_, Jan 04 2012

%E a(11) from Peter Österlund on Feb 22 2013, verified by _François Labelle_ on Jan 08 2017