OFFSET
1,2
LINKS
Mathilde Bouvel, Philippe Gambette and Marefatollah Mansouri, Maple worksheet
Mathilde Bouvel, Philippe Gambette and Marefatollah Mansouri, Counting Phylogenetic Networks of level 1 and 2, arXiv:1909.10460 [math.CO], 2019.
Charles Semple and Mike Steel, Unicyclic networks: compatibility and enumeration, Transactions on Computational Biology and Bioinformatics (3:1 pp.398--401), 2006.
FORMULA
Semple and Steele provide a summation formula for a(n) (see their Theorem 4).
Bouvel, Gambette and Mansouri provide (among other additional results) an equation for the associated exponential generating function, and an asymptotic estimate of a(n). See their Section 4.
EXAMPLE
a(4) = 192 is the number of unrooted level-1 phylogenetic networks with 5 labeled leaves
MAPLE
# see links section
CROSSREFS
KEYWORD
nonn
AUTHOR
Mathilde Bouvel, Oct 04 2019
STATUS
approved