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A294240
The number of possible ways in which 2*n^2 black pawns and 2*n^2 white pawns can be arranged on a 2n X 2n chessboard such that no pawn attacks another.
0
1, 3, 30, 410, 6148, 96120, 1526700, 24425026, 392143828, 6306613690, 101505099104, 1634209596410, 26311180850268, 423567557239604, 6817440328754244, 109703307312544664, 1764863031686159684, 28385338557467333804, 456426743658724223028, 7337464027218416593362
OFFSET
0,2
COMMENTS
White pawns attack diagonally up and black pawns attack diagonally down.
En passant capturing is not possible.
LINKS
Code Golf Stack Exchange user feersum, Too many pawns on a chess board.
EXAMPLE
For n = 1 the a(1) = 3 boards are as follows:
+---+---+ +---+---+ +---+---+
| W | W | | B | W | | W | B |
+---+---+ +---+---+ +---+---+
| B | B | | W | B | | B | W |
+---+---+ +---+---+ +---+---+
.
An example of one of the a(2) = 30 boards is:
+---+---+---+---+
| W | W | W | W |
+---+---+---+---+
| B | W | W | W |
+---+---+---+---+
| B | B | W | B |
+---+---+---+---+
| B | B | B | B |
+---+---+---+---+
CROSSREFS
Cf. A035290.
Sequence in context: A234506 A212425 A336538 * A007004 A354291 A354287
KEYWORD
nonn
AUTHOR
Peter Kagey, Oct 25 2017
STATUS
approved