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 A097998 #12 Feb 12 2021 19:43:20
%S A097998 1,1,1,4,37,602,14436,458062,18029992,845360028,45938606320,
%T A097998 2836966508216,196156795008384,15008752290350656,1258841795197091392,
%U A097998 114838947237881287800,11319937495659268412416,1198945386491423345685968,135784713567893046210563328
%N A097998 Number of connected outerplanar graphs on n labeled nodes.
%H A097998 Andrew Howroyd, <a href="/A097998/b097998.txt">Table of n, a(n) for n = 0..200</a>
%H A097998 M. Bodirsky and M. Kang, <a href="http://www.informatik.hu-berlin.de/~bodirsky/publications/asymptoticBK.html">The asymptotic number of outerplanar graphs</a>.
%H A097998 S. R. Finch, <a href="http://www.people.fas.harvard.edu/~sfinch/">Planar graph growth constants</a>.
%H A097998 Steven R. Finch, <a href="/A097999/a097999.pdf">Planar graph growth constants</a> [Cached copy, with permission of the author]
%F A097998 Recurrence known, see Bodirsky and Kang.
%o A097998 (PARI) seq(n)={Vec(serlaplace(1 + intformal(serreverse(x/exp((1 + 5*x - sqrt(1 - 6*x + x^2 + O(x^n)))/8))/x)))} \\ _Andrew Howroyd_, Feb 12 2021
%Y A097998 Cf. A097999, A098000, A111563.
%K A097998 nonn
%O A097998 0,4
%A A097998 _Steven Finch_, Sep 08 2004
%E A097998 a(0)=1 prepended and terms a(17) and beyond from _Andrew Howroyd_, Feb 12 2021