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 A339647 #6 Dec 16 2020 19:26:05
%S A339647 0,1,3,17,73,369,1795,9192,47324,249164,1326449,7155620,38979373,
%T A339647 214304435,1187338427,6624057963,37178881395,209802434879,
%U A339647 1189621738769,6774546637528,38729276531965,222191966031306,1278819536137209,7381798618249920,42724974018583842
%N A339647 Number of inequivalent leaf colorings of series-reduced planted trees with n leaves using exactly 2 colors.
%C A339647 Equivalence is up to permutation of the colors.
%e A339647 a(2) = 1: (12).
%e A339647 a(3) = 3: (112), (1(12)), (1(22)).
%e A339647 a(4) = 17: (1112), (1122), (11(12)), (11(22)), (12(11)), (12(12)), (1(112)), (1(122)), (1(222)), (1(1(12))), (1(1(22))), (1(2(11))), (1(2(12))), (1(2(22))), ((11)(12)), ((11)(22)), ((12)(12)).
%o A339647 (PARI) \\ See A339647 for cycleIndexSeries and InequivalentColoringsSeq.
%o A339647 { my(S=cycleIndexSeries(20)); InequivalentColoringsSeq(S,2) - InequivalentColoringsSeq(S,1) }
%Y A339647 The case that colors may not be interchanged is A319377.
%Y A339647 Column 2 of A339645.
%Y A339647 Cf. A000669, A339646.
%K A339647 nonn
%O A339647 1,3
%A A339647 _Andrew Howroyd_, Dec 16 2020