= Wedderburn–Etherington number
{wiki=Wedderburn–Etherington_number}
The Wedderburn–Etherington numbers are a sequence of integers that count certain types of binary trees, specifically the number of distinct full binary trees (or proper binary trees) with a given number of internal nodes. A full binary tree is a tree in which every internal node has exactly two children. The \\( n \\)-th Wedderburn–Etherington number counts the number of full binary trees with \\( n \\) internal nodes.
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