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A320172 Number of series-reduced balanced rooted identity trees whose leaves are integer partitions whose multiset union is an integer partition of n. 4
1, 2, 5, 9, 19, 38, 79, 163, 352, 750, 1633, 3558, 7783, 17020, 37338, 81920, 180399, 398600, 885101, 1975638, 4435741, 10013855, 22726109, 51807432, 118545425, 272024659, 625488420, 1440067761, 3317675261, 7644488052, 17610215982, 40547552277, 93298838972, 214516498359, 492844378878 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

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. In an identity tree, all branches directly under any given node are different.

LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..500

EXAMPLE

The a(1) = 1 through a(5) = 19 rooted identity trees:

  (1)  (2)   (3)        (4)         (5)

       (11)  (21)       (22)        (32)

             (111)      (31)        (41)

             ((1)(2))   (211)       (221)

             ((1)(11))  (1111)      (311)

                        ((1)(3))    (2111)

                        ((1)(21))   (11111)

                        ((2)(11))   ((1)(4))

                        ((1)(111))  ((2)(3))

                                    ((1)(31))

                                    ((1)(22))

                                    ((2)(21))

                                    ((3)(11))

                                    ((1)(211))

                                    ((11)(21))

                                    ((2)(111))

                                    ((1)(1111))

                                    ((11)(111))

                                    ((1)(2)(11))

MATHEMATICA

sps[{}]:={{}}; sps[set:{i_, ___}]:=Join@@Function[s, Prepend[#, s]&/@sps[Complement[set, s]]]/@Cases[Subsets[set], {i, ___}];

mps[set_]:=Union[Sort[Sort/@(#/.x_Integer:>set[[x]])]&/@sps[Range[Length[set]]]];

gig[m_]:=Prepend[Join@@Table[Union[Sort/@Select[Sort/@Tuples[gig/@mtn], UnsameQ@@#&]], {mtn, Select[mps[m], Length[#]>1&]}], m];

Table[Sum[Length[Select[gig[y], SameQ@@Length/@Position[#, _Integer]&]], {y, Sort /@IntegerPartitions[n]}], {n, 8}]

PROG

(PARI) WeighT(v)={Vec(exp(x*Ser(dirmul(v, vector(#v, n, (-1)^(n-1)/n))))-1, -#v)}

seq(n)={my(u=vector(n, n, numbpart(n)), v=vector(n)); while(u, v+=u; u=WeighT(u)-u); v} \\ Andrew Howroyd, Oct 25 2018

CROSSREFS

Cf. A000669, A005804, A048816, A079500, A119262, A120803, A141268, A292504, A300660, A319312.

Cf. A320154, A320155, A320160, A320171, A320173, A320177, A320178, A320179.

Sequence in context: A178841 A214319 A062092 * A079117 A030137 A243080

Adjacent sequences:  A320169 A320170 A320171 * A320173 A320174 A320175

KEYWORD

nonn

AUTHOR

Gus Wiseman, Oct 07 2018

EXTENSIONS

Terms a(13) and beyond from Andrew Howroyd, Oct 25 2018

STATUS

approved

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Last modified September 18 21:51 EDT 2021. Contains 347536 sequences. (Running on oeis4.)