A320173 Number of inequivalent colorings of series-reduced balanced rooted trees with n leaves.

1, 2, 3, 12, 23, 84, 204, 830, 2940, 13397, 58794, 283132, 1377302, 7087164, 37654377, 209943842, 1226495407, 7579549767, 49541194089, 341964495985, 2476907459261, 18703210872343, 146284738788714, 1179199861398539, 9760466433602510, 82758834102114911, 717807201648148643

Offset: 1

Author

Gus Wiseman, Oct 07 2018

Keywords

• nonn

Comments

A rooted tree is series-reduced if every non-leaf node has at least two branches, and balanced if all leaves are the same distance from the root.

Examples

			Inequivalent representatives of the a(1) = 1 through a(5) = 23 colorings:
  1  (11)  (111)    (1111)      (11111)
     (12)  (112)    (1112)      (11112)
           (123)    (1122)      (11122)
                    (1123)      (11123)
                    (1234)      (11223)
                  ((11)(11))    (11234)
                  ((11)(12))    (12345)
                  ((11)(22))  ((11)(111))
                  ((11)(23))  ((11)(112))
                  ((12)(12))  ((11)(122))
                  ((12)(13))  ((11)(123))
                  ((12)(34))  ((11)(223))
                              ((11)(234))
                              ((12)(111))
                              ((12)(112))
                              ((12)(113))
                              ((12)(123))
                              ((12)(134))
                              ((12)(345))
                              ((13)(122))
                              ((22)(111))
                              ((23)(111))
                              ((23)(114))
		

Crossrefs

Cf. A000669, A005804, A048816, A079500, A119262, A120803, A141268, A244925, A319312.

Cf. A320154, A320155, A320160, A320174, A320175, A320179, A339645.

Programs

PARI

\\ See links in A339645 for combinatorial species functions.
cycleIndexSeries(n)={my(p=x*sv(1) + O(x*x^n), q=0); while(p, q+=p; p=sEulerT(p)-1-p); q}
InequivalentColoringsSeq(cycleIndexSeries(15)) \\ Andrew Howroyd, Dec 11 2020

Extensions

Terms a(8) and beyond from Andrew Howroyd, Dec 11 2020