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A177554
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Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down.
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0
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1, 4, 28, 304, 4576, 91072, 2306176, 71993344, 2707268608, 120392433664, 6235322515456, 371376015818752, 25166910597922816, 1922787147517394944, 164313634414773403648
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OFFSET
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1,2
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LINKS
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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