login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo

Please make a donation to keep the OEIS running. We are now in our 56th year. In the past year we added 10000 new sequences and reached almost 9000 citations (which often say "discovered thanks to the OEIS").
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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: A182512 A075869 A307369 * 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 25 20:20 EST 2020. Contains 338627 sequences. (Running on oeis4.)