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A272070

Number of ways to quarter a 2n+1 X 2n+1 chessboard with central square removed.

1, 7, 104, 3970, 431932, 137066448, 128095791922, 355704307903818, 2952926822418475378, 73569487283165427567144, 5515501712040561162370942752, 1246743475892797935712690352483842, 850999652841310762943520023896881419780

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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.

LINKS

Table of n, a(n) for n=1..13.

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

Cf. A006067, A064941, A257952.

Sequence in context: A001921 A215552 A357344 * A098362 A093741 A139742

Adjacent sequences: A272067 A272068 A272069 * A272071 A272072 A272073

KEYWORD

nonn

AUTHOR

Andrew Howroyd, Apr 19 2016

STATUS

approved