 | ECS #43: Non plane rooted binary trees |
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1. Description
unlabelled binary rooted trees with n endpoints inequivalent under reflections in vertical axes. (Wedderburn-Etherington numbers)
2. Specification
This unlabelled structure is specified as S in
\displaystyle
\left\{ S={\rm Union} \left( Z,{\rm Set} \left( S,{\rm card}=2
\right) \right) \right\}
other formats
3. Coefficients
3.1. First terms
4. Ordinary generating function
\displaystyle
[S \left( x \right) =x+1/2\,S \left( {x}^{2} \right) +1/2\, \left( S
\left( x \right) \right) ^{2},Z \left( x \right) =x]
other formats
5. References
6. Random structure
Search a combinatorial structure by: (firstTerms should be a sequence of integers, separated by commas).