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A226968
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Number of labeled octopi with n nodes such that each tentacle has an odd number of nodes.
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3
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0, 1, 1, 8, 30, 264, 1920, 20880, 226800, 3064320, 43908480, 722131200, 12773376000, 249559833600, 5236924492800, 118911189196800, 2883421981440000, 74715282690048000, 2054450584682496000, 59855791774851072000, 1839882143683584000000
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OFFSET
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0,4
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LINKS
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FORMULA
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For n>=1; (n-1)!*( A000032(n) + (-1)^(n+1) -1 ).
E.g.f.: log(1/(1 - A(x)) where A(x) = x/(1-x^2).
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MATHEMATICA
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nn=20; f[x_]:=x/(1-x^2); Range[0, nn]!CoefficientList[Series[Log[1/(1-f[x])], {x, 0, nn}], x]
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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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