OFFSET
1,3
COMMENTS
Consider an n X n chessboard. Place n queens in the cells of the first row, in cells (1,1), (2,1),..., (n,1) and [(n+1)/2] pawns in the odd cells of the second row, namely in cells (1,2), (3,2), (5,2), ... Sequence gives the number of cells that are not attacked by the queens.
REFERENCES
Suggested by a chessboard problem from Antreas P. Hatzipolakis.
LINKS
Index entries for linear recurrences with constant coefficients, signature (1,1,-1,1,-1,-1,1).
FORMULA
G.f. x^3(x^4 - x^3 - x^2 - 2x - 2)/((x-1)^3*(x+1)^2*(x^2+1)). - Ralf Stephan, Jul 25 2003
MAPLE
f := [0, 0]: for i from 3 by 2 to 60 do f := [op(f), ((i-1)/2)^2 - 1 + floor((i-1)/4)*ceil((i-1)/4)]: f := [op(f), f[nops(f)] + (i+1)/2]: od: f;
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Len Smiley, Jun 02 2000
EXTENSIONS
More terms from Asher Auel
STATUS
approved