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A126685 In chess, the number of checkmate dual-free proof games in n plies. 0
0, 0, 0, 0, 0, 3, 51, 1106, 3813, 47300, 216420, 2057581, 10276981, 74358924 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,6
COMMENTS
Among all the proof game problems counted in A090051, this is the number of problems ending in checkmate.
LINKS
Retrograde Analysis Corner, Shortest Mates in Proof Games.
EXAMPLE
a(5)=3 because there are three checkmate proof games in 5 plies:
1. e4 e5 2. Qh5 Ke7 3. Qxe5#
1. e3 e5 2. Qh5 Ke7 3. Qxe5#
1. e4 f5 2. exf5 g5 3. Qh5#
CROSSREFS
Sequence in context: A075869 A361051 A307369 * A355797 A246693 A187666
KEYWORD
hard,nonn,fini
AUTHOR
François Labelle, Feb 13 2007
EXTENSIONS
a(12)-a(13) from François Labelle, Dec 05 2017
STATUS
approved

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Last modified March 29 03:51 EDT 2024. Contains 371264 sequences. (Running on oeis4.)