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A078993 Starting at the chess position shown, a(n) is the number of ways Black can make n consecutive moves, followed by a checkmate in one move by White. +0
1
0, 0, 0, 0, 0, 2, 11, 35, 118, 354, 1080, 3207, 9564, 28340, 84065, 248990, 737659, 2184639, 6470361, 19162095, 56749647, 168064304, 497724596, 1474011695, 4365289531, 12927804291, 38285696466, 113383077705, 335783959965, 994424075606, 2944986563117, 8721576611648 (list; graph; listen)
OFFSET

0,6

COMMENT

Starting position: White queen at g7, king at h1; Black pawn at h7, king at h6. Black may not move into check.

REFERENCES

Problem composed by N. D. Elkies.

LINKS

R. P. Stanley, Extremal [Chess] Problems

FORMULA

G.f.: x^5*(2+5*x-4*x^2-2*x^3)/((1-x^2)*(1-2*x^2)*(1-3*x+x^4)).

CROSSREFS

Sequence in context: A000914 A086735 A078982 this_sequence A071244 A005583 A015519

Adjacent sequences: A078990 A078991 A078992 this_sequence A078994 A078995 A078996

KEYWORD

nonn

AUTHOR

njas, Jan 18 2003

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Last modified August 29 17:54 EDT 2008. Contains 143238 sequences.


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