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A177557
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Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, up.
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0
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1, 5, 55, 1062, 31147, 1313796, 75373533, 5661748406, 539467979009, 63618193828712, 9098617148960622, 1551945898935373561, 311275951583298747596, 72535753321856685723563
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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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