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A122647
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Number of permutations of length 2*n-1 with no local maxima or minima in even positions.
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3
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1, 2, 14, 204, 5104, 195040, 10570416, 771171296, 72871890176, 8658173200896, 1263326817241600, 222078432102900736, 46291130226003357696, 11289508838355990634496, 3184719803676823556888576, 1028950134725811309304442880, 377483869192551997938994315264, 156057810922284533544621710639104
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OFFSET
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1,2
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LINKS
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FORMULA
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MAPLE
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egf:= (x->1/(1-x*tanh(x))-1)(z/sqrt(2)):
a:= n-> (2*n)!/n*coeff(series(egf, z, 2*n+1), z, 2*n):
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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