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A209433
Number of chess diagrams that can be obtained in n plies, but not in fewer plies.
1
1, 20, 400, 5202, 69731, 766337, 8708079, 86540204, 880526165, 7996545696, 73802185449, 616052245142
OFFSET
0,2
COMMENTS
Chess diagrams are chess positions without regard to whether castling or en passant capturing is possible. The condition that the diagram cannot be obtained in fewer than n plies means that each legal chess diagram is counted exactly once in this sequence, indexed by the length of the shortest game(s) to reach it. Therefore, this sequence is finite and its sum equals the number of legal chess diagrams, estimated to be between 10^43 and 10^47.
CROSSREFS
Sequence in context: A207091 A223988 A189698 * A188988 A019319 A083276
KEYWORD
nonn,hard,fini,more
AUTHOR
François Labelle, Mar 08 2012
EXTENSIONS
a(11) from François Labelle, Feb 27 2017
STATUS
approved