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%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&p=508645&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
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