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 A339646 #8 Dec 16 2020 19:25:54 %S A339646 1,2,5,22,85,402,1885,9453,48090,251476,1333517,7177585,39048327, %T A339646 214523186,1188037961,6626311639,37186187183,209826251622, %U A339646 1189699762371,6774803376279,38730124684829,222194778028278,1278828889503773,7381829822338301,42725078403203912 %N A339646 Number of inequivalent leaf colorings of series-reduced planted trees with n leaves using at most 2 colors. %C A339646 Equivalence is up to permutation of the colors. %F A339646 a(n) = A339647(n) - A000669(n). %e A339646 a(1) = 1: 1. %e A339646 a(2) = 2: (11), (12). %e A339646 a(3) = 5: (111), (112), (1(11)), (1(12)), (1(22)). %o A339646 (PARI) \\ See A339645 for cycleIndexSeries and InequivalentColoringsSeq. %o A339646 InequivalentColoringsSeq(cycleIndexSeries(20),2) %Y A339646 The case that colors may not be interchanged is A050381. %Y A339646 Cf. A000669, A339645, A339647. %K A339646 nonn %O A339646 1,2 %A A339646 _Andrew Howroyd_, Dec 16 2020