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 A328123 #18 Feb 03 2020 05:55:36 %S A328123 1,9,282,14697,1071750,100467405,11509922970,1558302613245, %T A328123 243426592473750,43095781327975425,8527098853816839450, %U A328123 1864790504534293823025,446647359698685492697350,116281255808439040209815925,32694665144001284972518220250 %N A328123 Number of unrooted level-2 phylogenetic networks with (n+1) labeled leaves, when multiple (i.e. parallel) edges are allowed. %H A328123 Mathilde Bouvel, Philippe Gambette and Marefatollah Mansouri, <a href="http://user.math.uzh.ch/bouvel/publications/BouvelGambetteMansouri_Version1_WithMultipleEdges.mw">Maple worksheet</a> %H A328123 Mathilde Bouvel, Philippe Gambette and Marefatollah Mansouri, <a href="https://arxiv.org/abs/1909.10460v2">Counting Phylogenetic Networks of level 1 and 2</a>, Version 2, arXiv:1909.10460 [math.CO], 2019. %F A328123 Bouvel, Gambette and Mansouri provide (among other results) a closed formula for a(n), an equation for the associated exponential generating function, and an asymptotic estimate of a(n). See their Section 6. %e A328123 a(3) = 282 is the number of unrooted level-2 phylogenetic networks with 4 labeled leaves. %p A328123 # see links section %Y A328123 Cf. A328121, A328122, A328126. %K A328123 nonn %O A328123 1,2 %A A328123 _Mathilde Bouvel_, Oct 04 2019 %E A328123 Name clarified by _Mathilde Bouvel_, Feb 03 2020