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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

Table of n, a(n) for n=0..20.

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

Adjacent sequences:  A226965 A226966 A226967 * A226969 A226970 A226971

KEYWORD

nonn

AUTHOR

Geoffrey Critzer, Sep 01 2013

STATUS

approved

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Last modified June 30 02:41 EDT 2022. Contains 354913 sequences. (Running on oeis4.)