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A189837 Number of ways to place n nonattacking composite pieces rook + rider[1,2] on an n X n chessboard. 6
1, 2, 2, 8, 12, 22, 58, 276, 648, 2304, 6508, 24528, 96402, 466922, 2271738, 13723826, 76579326, 512425626, 3281233020, 24654941268, 175398054696 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

(in fairy chess the rider [1,2] is called a Nightrider, Rook + Nightrider = Waran)

a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+k)-p(i)|<>2k AND |p(j+2k)-p(j)|<>k for all i>=1, j>=1, k>=1, i+k<=n, j+2k<=n

LINKS

Table of n, a(n) for n=1..21.

V. Kotesovec, Number of ways of placing non-attacking queens, kings, bishops and knights (in English and Czech)

Wikipedia, Fairy chess piece

CROSSREFS

Cf. A102388, A000170

Sequence in context: A008828 A254219 A053414 * A274409 A302118 A014236

Adjacent sequences:  A189834 A189835 A189836 * A189838 A189839 A189840

KEYWORD

nonn,hard

AUTHOR

Vaclav Kotesovec, Apr 29 2011

STATUS

approved

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Last modified November 26 03:20 EST 2020. Contains 338632 sequences. (Running on oeis4.)