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 A301700 #31 Sep 01 2018 21:27:52
%S A301700 1,1,1,2,4,10,21,52,120,290,697,1713,4200,10446,26053,65473,165257,
%T A301700 419357,1068239,2732509,7013242,18059960,46641983,120790324,313593621,
%U A301700 816046050,2128101601,5560829666,14557746453,38177226541,100281484375,263815322761,695027102020
%N A301700 Number of aperiodic rooted trees with n nodes.
%C A301700 An unlabeled rooted tree is aperiodic if the multiset of branches of the root is an aperiodic multiset, meaning it has relatively prime multiplicities, and each branch is also aperiodic.
%H A301700 Andrew Howroyd, <a href="/A301700/b301700.txt">Table of n, a(n) for n = 1..500</a>
%e A301700 The a(6) = 10 aperiodic trees are (((((o))))), (((o(o)))), ((o((o)))), ((oo(o))), (o(((o)))), (o(o(o))), ((o)((o))), (oo((o))), (o(o)(o)), (ooo(o)).
%t A301700 arut[n_]:=arut[n]=If[n===1,{{}},Join@@Function[c,Select[Union[Sort/@Tuples[arut/@c]],GCD@@Length/@Split[#]===1&]]/@IntegerPartitions[n-1]];
%t A301700 Table[Length[arut[n]],{n,20}]
%o A301700 (PARI) EulerT(v)={Vec(exp(x*Ser(dirmul(v,vector(#v,n,1/n))))-1, -#v)}
%o A301700 MoebiusT(v)={vector(#v, n, sumdiv(n,d,moebius(n/d)*v[d]))}
%o A301700 seq(n)={my(v=[1]); for(n=2, n, v=concat([1], MoebiusT(EulerT(v)))); v} \\ _Andrew Howroyd_, Sep 01 2018
%Y A301700 Cf. A000081, A000740, A000837, A001678, A003238, A004111, A007716, A007916, A100953, A276625, A284639, A290689, A298422, A303386, A303431.
%K A301700 nonn
%O A301700 1,4
%A A301700 _Gus Wiseman_, Apr 23 2018
%E A301700 Terms a(21) and beyond from _Andrew Howroyd_, Sep 01 2018