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A339646
Number of inequivalent leaf colorings of series-reduced planted trees with n leaves using at most 2 colors.
1
1, 2, 5, 22, 85, 402, 1885, 9453, 48090, 251476, 1333517, 7177585, 39048327, 214523186, 1188037961, 6626311639, 37186187183, 209826251622, 1189699762371, 6774803376279, 38730124684829, 222194778028278, 1278828889503773, 7381829822338301, 42725078403203912
OFFSET
1,2
COMMENTS
Equivalence is up to permutation of the colors.
FORMULA
a(n) = A339647(n) - A000669(n).
EXAMPLE
a(1) = 1: 1.
a(2) = 2: (11), (12).
a(3) = 5: (111), (112), (1(11)), (1(12)), (1(22)).
PROG
(PARI) \\ See A339645 for cycleIndexSeries and InequivalentColoringsSeq.
InequivalentColoringsSeq(cycleIndexSeries(20), 2)
CROSSREFS
The case that colors may not be interchanged is A050381.
Sequence in context: A346557 A288028 A083465 * A215100 A307155 A144934
KEYWORD
nonn
AUTHOR
Andrew Howroyd, Dec 16 2020
STATUS
approved