OFFSET
0,5
COMMENTS
a(6) was computed in 1897.
REFERENCES
H. Simpson, Chess Review, Jan-Feb 1982.
LINKS
F. Labelle,Statistics on chess games
R. P. Stanley,Extremal [Chess] Problems
M. Willey,Iowa Chess Homepage.
World Chess Federation,Laws of Chess: For competitions starting on or after 1 July 2014
J. Young,Opening Tree Statistics.
EXAMPLE
a(n) = 0 for n < 4 and a(4) = 8, because the earliest checkmate can occur at move 2, e.g., with 1.f3 e5, 2.g4 Qh4#. The 8 = 2*2*2 possibilities counted in a(4) all correspond to essentially the same mate, with (1) the alternative 1.f4, (2) the alternative 1...e6, (3) inversed order of white's moves. -M. F. Hasler, Mar 03 2022
CROSSREFS
KEYWORD
nonn,hard,more,nice,fini
AUTHOR
N. J. A. Sloane, Jan 17 2003
EXTENSIONS
More terms fromRichard Bean, Jun 08 2003
a(9) and a(10) fromFrançois Labelle, Jan 12 2004
a(11) fromFrançois Labelle, Jul 25 2004, who thanks Joost de Heer for providing computer time.
Link to Extremal [Chess] Problems of R. P. Stanley corrected byJohannes W. Meijer, Mar 01 2009
a(12) fromFrançois Labelle, Mar 04 2012
a(13) fromFrançois Labelle, Aug 15 2017
STATUS
approved