4074381

Appears in sequences

• a(n) = (2n + 1)*3^n.at n=11A124647
• The number of nonequivalent root ancestral configurations in a recursively defined family of gene trees and species trees with at least n = 9 leaves, in which for n >= 12 leaves, 3-leaf trees are successively added at the root of the tree with n-3 leaves.at n=33A355118