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A055607 a(2n+1) = n^2 - 1 + A002620(n), a(2n) = a(2n-1) + n. 0
0, 0, 2, 4, 7, 10, 14, 19, 24, 30, 36, 44, 51, 60, 68, 79, 88, 100, 110, 124, 135, 150, 162, 179, 192, 210, 224, 244, 259, 280, 296, 319, 336, 360, 378, 404, 423, 450, 470, 499, 520, 550, 572, 604, 627, 660, 684, 719, 744, 780, 806, 844, 871, 910, 938, 979, 1008 (list; graph; refs; listen; history; text; internal format)
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
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
Sequence in context: A127723 A076268 A323623 * A024512 A047808 A007980
KEYWORD
nonn,easy
AUTHOR
Len Smiley, Jun 02 2000
EXTENSIONS
More terms from Asher Auel
STATUS
approved

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Last modified April 18 11:52 EDT 2024. Contains 371779 sequences. (Running on oeis4.)