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Wedderburn-Etherington number
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(Definition)
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The  th Wedderburn-Etherington number counts how many weakly binary trees can be constructed such that each graph vertex (not counting the root vertex) is adjacent to no more than three other such vertices, for a given number
 of nodes. The first few Wedderburn-Etherington numbers are 1, 1, 1, 2, 3, 6, 11, 23, 46, 98, 207, 451, 983, etc. listed in A001190 of Sloane's OEIS. Michael Somos gives the following recurrence relations:
and
with
 in both relations.
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"Wedderburn-Etherington number" is owned by PrimeFan.
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(view preamble | get metadata)
| Other names: |
Wedderburn Etherington number, Etherington-Wedderburn number |
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Cross-references: relations, recurrence relations, OEIS, nodes, number, vertices, adjacent, root, vertex, graph, binary trees
There is 1 reference to this entry.
This is version 3 of Wedderburn-Etherington number, born on 2007-03-11, modified 2007-03-16.
Object id is 9064, canonical name is WedderburnEtheringtonNumber.
Accessed 1271 times total.
Classification:
| AMS MSC: | 05A15 (Combinatorics :: Enumerative combinatorics :: Exact enumeration problems, generating functions) |
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Pending Errata and Addenda
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