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A226968
Number of labeled octopi with n nodes such that each tentacle has an odd number of nodes.
3
0, 1, 1, 8, 30, 264, 1920, 20880, 226800, 3064320, 43908480, 722131200, 12773376000, 249559833600, 5236924492800, 118911189196800, 2883421981440000, 74715282690048000, 2054450584682496000, 59855791774851072000, 1839882143683584000000
OFFSET
0,4
FORMULA
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).
MATHEMATICA
nn=20; f[x_]:=x/(1-x^2); Range[0, nn]!CoefficientList[Series[Log[1/(1-f[x])], {x, 0, nn}], x]
CROSSREFS
Cf. A029767.
Sequence in context: A098741 A027146 A302409 * A303679 A304218 A304130
KEYWORD
nonn,changed
AUTHOR
Geoffrey Critzer, Sep 01 2013
STATUS
approved