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 A108531 #9 Jun 20 2018 16:35:11
%S A108531 1,2,6,18,60,206,770,2950,11748,47746,197808,830878,3532790,15168294,
%T A108531 65683552,286504378,1257693038,5551978426,24630911086,109759215338,
%U A108531 491060888588,2204938828766,9933016712348,44881199711338
%N A108531 Number of mobiles (cycle rooted trees) with n nodes and 2-colored internal (non-leaf) nodes.
%H A108531 Andrew Howroyd, <a href="/A108531/b108531.txt">Table of n, a(n) for n = 1..200</a>
%H A108531 <a href="/index/Mo#mobiles">Index entries for sequences related to mobiles</a>
%H A108531 C. G. Bower, <a href="/transforms2.html">Transforms (2)</a>
%F A108531 Shifts left and halves under CIK transform.
%o A108531 (PARI)
%o A108531 CIK(p,n)={sum(d=1, n, eulerphi(d)/d*log(subst(1/(1+O(x*x^(n\d))-p), x, x^d)))}
%o A108531 seq(n)={my(p=O(1));for(i=1, n, p=1+2*CIK(x*p, i)); Vec(p)} \\ _Andrew Howroyd_, Jun 20 2018
%Y A108531 Cf. A032200, A108530, A108532.
%K A108531 nonn,eigen
%O A108531 1,2
%A A108531 _Christian G. Bower_, Jun 07 2005