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A368219
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Table read by antidiagonals: T(n,k) is the number of tilings of the n X k grid up to horizontal and vertical reflections by a tile that is fixed under 180-degree rotation but not horizontal or vertical reflection.
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5
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1, 2, 2, 3, 7, 3, 6, 20, 20, 6, 10, 76, 136, 76, 10, 20, 272, 1056, 1056, 272, 20, 36, 1072, 8256, 16576, 8256, 1072, 36, 72, 4160, 65792, 262656, 262656, 65792, 4160, 72, 136, 16576, 524800, 4197376, 8390656, 4197376, 524800, 16576, 136
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OFFSET
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1,2
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LINKS
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EXAMPLE
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Table begins:
n\k | 1 2 3 4 5 6
----+--------------------------------------------
1 | 1 2 3 6 10 20
2 | 2 7 20 76 272 1072
3 | 3 20 136 1056 8256 65792
4 | 6 76 1056 16576 262656 4197376
5 | 10 272 8256 262656 8390656 268451840
6 | 20 1072 65792 4197376 268451840 17180065792
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MATHEMATICA
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A368219[n_, m_] := 2^(n*m/2 - 2)*(2^(n*m/2) + If[EvenQ[n*m], 1, Sqrt[2]] + Boole[EvenQ[n]] + Boole[EvenQ[m]])
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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