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 A055540 #17 Feb 16 2025 08:32:43
%S A055540 0,2,4,14,38,153,766,6259,88064,2324157,116563882,11060411527,
%T A055540 1968703079886,654492092481733,406111248305672980,
%U A055540 471005105043787823717,1023566652048387537072658,4179937690541808658135640875,32172436158252943170541450460638
%N A055540 Total number of leaves (nodes of vertex degree 1) in all graphs of n nodes.
%H A055540 Andrew Howroyd, <a href="/A055540/b055540.txt">Table of n, a(n) for n = 1..50</a>
%H A055540 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/TreeLeaf.html">Tree Leaf</a>
%F A055540 a(n) = Sum_{k=1..n} k*A327371(n, k). - _Andrew Howroyd_, Sep 04 2019
%o A055540 (PARI) \\ See A327371 for G.
%o A055540 seq(n)=Vec(subst(deriv(G(n), y), y, 1), -n) \\ _Andrew Howroyd_, Jan 22 2021
%Y A055540 Cf. A003227, A003228, A055541, A327371.
%K A055540 nonn
%O A055540 1,2
%A A055540 _Eric W. Weisstein_
%E A055540 a(8) and a(9) from _Eric W. Weisstein_, Jun 02 2004
%E A055540 a(10) from _Andrew Howroyd_, Sep 04 2019
%E A055540 Terms a(11) and beyond from _Andrew Howroyd_, Jan 22 2021