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 A055291 #12 Mar 07 2022 10:22:22 %S A055291 1,2,4,8,14,23,36,54,78,110,150,201,264,341,433,544,674,827,1004,1209, %T A055291 1443,1711,2013,2355,2738,3167,3643,4173,4757,5402,6109,6885,7731, %U A055291 8655,9657,10746,11923,13196,14566,16043,17627,19328,21147,23094 %N A055291 Number of trees with n nodes and 4 leaves. %H A055291 Georg Fischer, <a href="/A055291/b055291.txt">Table of n, a(n) for n = 5..250</a> %H A055291 <a href="/index/Tra#trees">Index entries for sequences related to trees</a> %F A055291 G.f.: x^5(x^5+x^3+1)/[(1-x^3)(1+x^2)(1-x^2)^2(1-x)^2]. %Y A055291 Column 4 of A055290. %K A055291 nonn %O A055291 5,2 %A A055291 _Christian G. Bower_, May 09 2000