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A272070
Number of ways to quarter a 2n+1 X 2n+1 chessboard with central square removed.
1
1, 7, 104, 3970, 431932, 137066448, 128095791922, 355704307903818, 2952926822418475378, 73569487283165427567144, 5515501712040561162370942752, 1246743475892797935712690352483842, 850999652841310762943520023896881419780
OFFSET
1,2
COMMENTS
The chessboard must be dissected into four identical pieces. All solutions have 90-degree rotational symmetry and solutions that differ only by rotation or reflection are considered equivalent.
FORMULA
a(n) = A006067(2*n+1).
MATHEMATICA
A006067 = Import["https://oeis.org/A006067/b006067.txt", "Table"][[All, 2]];
a[n_] := A006067[[2n+1]];
a /@ Range[1, 13] (* Jean-François Alcover, Sep 14 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Andrew Howroyd, Apr 19 2016
STATUS
approved