This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A328121 #22 Apr 05 2020 04:23:44 %S A328121 1,2,15,192,3450,79740,2252880,75227040,2898481320,126570502800, %T A328121 6177380517000,333231084648000,19687828831070400,1264341183311606400, %U A328121 87691200344603856000,6532556443068591936000,520205544912884502672000,44098092640676115673632000,3964782594938523231457584000 %N A328121 Number of unrooted level-1 phylogenetic networks (also called galled trees) with (n+1) labeled leaves. %H A328121 Mathilde Bouvel, Philippe Gambette and Marefatollah Mansouri, <a href="http://user.math.uzh.ch/bouvel/publications/BouvelGambetteMansouri.mw">Maple worksheet</a> %H A328121 Mathilde Bouvel, Philippe Gambette and Marefatollah Mansouri, <a href="https://arxiv.org/abs/1909.10460">Counting Phylogenetic Networks of level 1 and 2</a>, arXiv:1909.10460 [math.CO], 2019. %H A328121 Charles Semple and Mike Steel, <a href="https://doi.org/10.1109/TCBB.2006.14">Unicyclic networks: compatibility and enumeration</a>, Transactions on Computational Biology and Bioinformatics (3:1 pp.398--401), 2006. %F A328121 Semple and Steele provide a summation formula for a(n) (see their Theorem 4). %F A328121 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. %e A328121 a(4) = 192 is the number of unrooted level-1 phylogenetic networks with 5 labeled leaves %p A328121 # see links section %Y A328121 Cf. A328122, A328123, A328126, A333005, A333006. %K A328121 nonn %O A328121 1,2 %A A328121 _Mathilde Bouvel_, Oct 04 2019