Counting Nonattacking Chess Piece Placements: Bishops and Anassas
Eder G. Santos
Brazil
Abstract:
We derive recurrences and closed-form expressions for counting
nonattacking placements of two types of chess pieces with unbounded
straight-line moves, namely the bishop (two diagonal moves) and the anassa
(one horizontal or vertical move and one diagonal move), placed on a
standard square chessboard. Additionally, we obtain explicit expressions
for the corresponding quasi-polynomial coefficients. The recurrences are
derived by analyzing how nonattacking configurations attack a specific
subset of board squares, employing a bijective argument to establish
the relations. The main results are simplifications of known expressions
for the bishop and a general counting formula for the anassa.
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(Concerned with sequences
A008277
A008299
A132393
A134991
A274105
A274106
A378561
A378590.)
Received January 22 2025; revised versions received January 30 2025; April 28 2025.
Published in Journal of Integer Sequences,
December 15 2025.
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