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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

Table of n, a(n) for n=0..13.

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: A145242 A182512 A075869 * A246693 A187666 A172434

Adjacent sequences:  A126682 A126683 A126684 * A126686 A126687 A126688

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 September 18 11:42 EDT 2018. Contains 315130 sequences. (Running on oeis4.)