A226968 Number of labeled octopi with n nodes such that each tentacle has an odd number of nodes.

0, 1, 1, 8, 30, 264, 1920, 20880, 226800, 3064320, 43908480, 722131200, 12773376000, 249559833600, 5236924492800, 118911189196800, 2883421981440000, 74715282690048000, 2054450584682496000, 59855791774851072000, 1839882143683584000000

Offset: 0

Author

Geoffrey Critzer, Sep 01 2013

Keywords

• nonn

Crossrefs

Cf. A029767.

Programs

Mathematica

nn=20;f[x_]:=x/(1-x^2);Range[0,nn]!CoefficientList[Series[Log[1/(1-f[x])],{x,0,nn}],x]

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).