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A177563
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Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, up, down, down.
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0
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1, 6, 88, 2328, 96886, 5841912, 482051408, 52197308928, 7182160372912, 1224288015648528, 253281233443497344, 62522722555285781376, 18154991497984902599824, 6126411246446756437747008
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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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