A126685 - OEIS

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A126685

In chess, the number of checkmate dual-free proof games in n plies.

0, 0, 0, 0, 0, 3, 51, 1106, 3813, 47300, 216420, 2057581 (list; graph; refs; listen; history; 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	`F. Labelle, Statistics on checkmate diagrams.` `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	`Cf. A090051, A102784.` `Sequence in context: A045489 A145242 A075869 * A187666 A172434 A105639` `Adjacent sequences: A126682 A126683 A126684 * A126686 A126687 A126688`
	KEYWORD	`hard,nonn`
	AUTHOR	`Francois Labelle (flab(AT)cs.berkeley.edu), Feb 13 2007`

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Last modified February 12 13:29 EST 2012. Contains 205412 sequences.