A214577 -id:A214577 - cp's OEIS frontend

A298536 Matula-Goebel numbers of rooted trees such that every branch of the root has a different number of leaves.

1, 2, 3, 5, 7, 11, 13, 14, 17, 19, 21, 23, 26, 29, 31, 34, 35, 37, 38, 39, 41, 43, 46, 47, 51, 53, 57, 58, 59, 61, 65, 67, 69, 71, 73, 74, 77, 79, 82, 83, 85, 86, 87, 89, 94, 95, 97, 101, 103, 106, 107, 109, 111, 113, 115, 118, 122, 123, 127, 129, 131, 133

Offset: 1

Gus Wiseman, Jan 20 2018

nonn

			Sequence of trees begins:
1  o
2  (o)
3  ((o))
5  (((o)))
7  ((oo))
11 ((((o))))
13 ((o(o)))
14 (o(oo))
17 (((oo)))
19 ((ooo))
21 ((o)(oo))
23 (((o)(o)))
26 (o(o(o)))
29 ((o((o))))
31 (((((o)))))
34 (o((oo)))
35 (((o))(oo))
37 ((oo(o)))
38 (o(ooo))
39 ((o)(o(o)))
41 (((o(o))))
43 ((o(oo)))
46 (o((o)(o)))
47 (((o)((o))))

Cf. A000081, A007097, A061775, A111299, A214577, A276625, A290689, A290760, A291442, A298534, A298535.

nn=2000;
primeMS[n_]:=If[n===1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
leafcount[n_]:=If[n===1,1,With[{m=primeMS[n]},If[Length[m]===1,leafcount[First[m]],Total[leafcount/@m]]]];
Select[Range[nn],UnsameQ@@leafcount/@primeMS[#]&]

A317099 Number of series-reduced planted achiral trees whose leaves span an initial interval of positive integers appearing with multiplicities an integer partition of n.

Original entry on oeis.org

1, 3, 4, 9, 8, 19, 16, 35, 35, 54, 57, 113, 102, 155, 189, 279, 298, 447, 491, 702, 813, 1063, 1256, 1759, 1967, 2542, 3050, 3902, 4566, 5882, 6843, 8676, 10205, 12612, 14908, 18608, 21638, 26510, 31292, 38150, 44584, 54185, 63262, 76308, 89371, 106818, 124755

Offset: 1

Gus Wiseman, Aug 01 2018

nonn

In these trees, achiral means that all branches directly under any given node that is not a leaf or a cover of leaves are equal, and series-reduced means that every node that is not a leaf or a cover of leaves has at least two branches.

			The a(4) = 9 trees:
  (1111), ((11)(11)), (((1)(1))((1)(1))), ((1)(1)(1)(1)),
  (1112),
  (1122), ((12)(12)),
  (1123),
  (1234).
The a(6) = 19 trees:
  (111111), ((111)(111)), (((1)(1)(1))((1)(1)(1))), ((11)(11)(11)), (((1)(1))((1)(1))((1)(1))), ((1)(1)(1)(1)(1)(1)),
  (111112),
  (111122), ((112)(112)),
  (111123),
  (111222), ((12)(12)(12)),
  (111223),
  (111234),
  (112233), ((123)(123)),
  (112234),
  (112345),
  (123456).

Cf. A001678, A003238, A052409, A052410, A067824, A167865, A168532, A214577, A289078, A294336, A316782, A317100.

b[n_]:=1+Sum[b[n/d],{d,Rest[Divisors[n]]}];
a[n_]:=Sum[b[GCD@@Length/@Split[ptn]],{ptn,IntegerPartitions[n]}];
Array[a,30]

A317853 a(1) = 1; a(n > 1) = Sum_{0 < k < n} (-1)^(n - k - 1) a(n - k) Sum_{d|k} a(d).

Original entry on oeis.org

1, 1, 1, 1, 2, 2, 5, 6, 11, 14, 23, 26, 51, 70, 114, 147, 237, 314, 516, 715, 1118, 1549, 2353, 3252, 5011, 7235, 10724, 15142, 22504, 32506, 47770, 69173, 100980, 146657, 212504, 308563, 448256, 658037, 946166, 1373739, 1988283, 2919185, 4197886, 6118850

Offset: 1

Gus Wiseman, Aug 09 2018

nonn

Cf. A001003, A001678, A002033, A003238, A052893, A053492, A067824, A167865, A214577, A277996, A280000, A317875.
Cf. A317876, A317877, A317878, A317879, A317880, A317881.
Cf. A317882, A317883, A317884, A317885.

a[n_]:=a[n]=If[n==1,1,Sum[(-1)^(n-k-1)*a[n-k]*Sum[a[d],{d,Divisors[k]}],{k,n-1}]];
Array[a,50]

A331991 Number of semi-lone-child-avoiding achiral rooted trees with n vertices.

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 3, 1, 3, 2, 4, 1, 5, 1, 5, 4, 4, 1, 7, 1, 7, 5, 6, 1, 7, 3, 7, 5, 7, 1, 13, 1, 8, 6, 6, 6, 10, 1, 9, 7, 9, 1, 15, 1, 12, 12, 8, 1, 12, 4, 13, 6, 11, 1, 15, 7, 13, 9, 9, 1, 17, 1, 15, 15, 9, 8, 21, 1, 13, 8, 16, 1, 18, 1, 12, 16, 11, 8, 21, 1

Offset: 1

Gus Wiseman, Feb 06 2020

nonn

A rooted tree is semi-lone-child-avoiding if there are no vertices with exactly one child unless that child is an endpoint/leaf.

In an achiral rooted tree, the branches of any given vertex are all equal.

			The a(n) trees for n = 2, 3, 5, 7, 11, 13:
  (o)  (oo)  (oooo)    (oooooo)     (oooooooooo)        (oooooooooooo)
             ((o)(o))  ((oo)(oo))   ((oooo)(oooo))      ((ooooo)(ooooo))
                       ((o)(o)(o))  ((o)(o)(o)(o)(o))   ((ooo)(ooo)(ooo))
                                    (((o)(o))((o)(o)))  ((oo)(oo)(oo)(oo))
                                                        ((o)(o)(o)(o)(o)(o))

Seiichi Manyama, Table of n, a(n) for n = 1..10000
David Callan, A sign-reversing involution to count labeled lone-child-avoiding trees, arXiv:1406.7784 [math.CO], (30-June-2014).
Gus Wiseman, Sequences counting series-reduced and lone-child-avoiding trees by number of vertices.

Matula-Goebel numbers of these trees are A331992.
The fully lone-child-avoiding case is A167865.
The semi-achiral version is A331933.
Not requiring achirality gives A331934.
The identity tree version is A331964.
The semi-identity tree version is A331993.
Achiral rooted trees are counted by A003238.
Lone-child-avoiding semi-achiral trees are A320268.
Cf. A000081, A004111, A050381, A001678, A214577, A289079, A320222, A331912, A331935, A331936, A331963, A331967, A331994.

ab[n_]:=If[n<=2,1,Sum[ab[d],{d,Most[Divisors[n-1]]}]];
Array[ab,100]

a(1) = a(2) = 1; a(n + 1) = Sum_{d|n, d 1.

G.f. A(x) satisfies: A(x) = x * (1 + (1/(1 + x)) * Sum_{k>=1} A(x^k)). - Ilya Gutkovskiy, Feb 25 2020

A331992 Matula-Goebel numbers of semi-lone-child-avoiding achiral rooted trees.

Original entry on oeis.org

1, 2, 4, 8, 9, 16, 27, 32, 49, 64, 81, 128, 243, 256, 343, 361, 512, 529, 729, 1024, 2048, 2187, 2401, 2809, 4096, 6561, 6859, 8192, 10609, 12167, 16384, 16807, 17161, 19683, 32768, 51529, 59049, 65536, 96721, 117649, 130321, 131072, 148877, 175561, 177147

Offset: 1

Gus Wiseman, Feb 06 2020

nonn

A rooted tree is semi-lone-child-avoiding if there are no vertices with exactly one child unless that child is an endpoint/leaf.
In an achiral rooted tree, the branches of any given vertex are all equal.
The Matula-Goebel number of a rooted tree is the product of primes indexed by the Matula-Goebel numbers of the branches of its root, which gives a bijective correspondence between positive integers and unlabeled rooted trees.
Consists of one, two, and all numbers of the form prime(j)^k where k > 1 and j is already in the sequence.

			The sequence of all semi-lone-child-avoiding achiral rooted trees together with their Matula-Goebel numbers begins:
     1: o
     2: (o)
     4: (oo)
     8: (ooo)
     9: ((o)(o))
    16: (oooo)
    27: ((o)(o)(o))
    32: (ooooo)
    49: ((oo)(oo))
    64: (oooooo)
    81: ((o)(o)(o)(o))
   128: (ooooooo)
   243: ((o)(o)(o)(o)(o))
   256: (oooooooo)
   343: ((oo)(oo)(oo))
   361: ((ooo)(ooo))
   512: (ooooooooo)
   529: (((o)(o))((o)(o)))
   729: ((o)(o)(o)(o)(o)(o))
  1024: (oooooooooo)

Gus Wiseman, Sequences counting series-reduced and lone-child-avoiding trees by number of vertices.
Gus Wiseman, The first 36 semi-lone-child-avoiding achiral rooted trees.

Except for two, a subset of A025475 (nonprime prime powers).
Not requiring achirality gives A331935.
The semi-achiral version is A331936.
The fully-chiral version is A331963.
The semi-chiral version is A331994.
The non-semi version is counted by A331967.
The enumeration of these trees by vertices is A331991.
Achiral rooted trees are counted by A003238.
MG-numbers of achiral rooted trees are A214577.
Cf. A001678, A007097, A050381, A061775, A167865, A196050, A276625, A280996, A291441, A291636, A320230, A320269, A331912, A331933, A331965.

msQ[n_]:=n<=2||!PrimeQ[n]&&Length[FactorInteger[n]]<=1&&And@@msQ/@PrimePi/@First/@FactorInteger[n];
Select[Range[10000],msQ]

Intersection of A214577 (achiral) and A331935 (semi-lone-child-avoiding).

A358508 Least Matula-Goebel number of a tree with exactly n permutations.

Original entry on oeis.org

1, 6, 12, 24, 48, 30, 192, 104, 148, 72, 3072, 60, 12288, 832, 144, 712, 196608, 222, 786432, 120, 288, 13312

Offset: 1

Gus Wiseman, Nov 20 2022

The Matula-Goebel number of a rooted tree is the product of primes indexed by the Matula-Goebel numbers of the branches of its root, which gives a bijective correspondence between positive integers and unlabeled rooted trees.

To get a permutation of a tree, we choose a permutation of the multiset of branches of each node.

			The terms together with their corresponding trees begin:
      1: o
      6: (o(o))
     12: (oo(o))
     24: (ooo(o))
     48: (oooo(o))
     30: (o(o)((o)))
    192: (oooooo(o))
    104: (ooo(o(o)))
    148: (oo(oo(o)))
     72: (ooo(o)(o))
   3072: (oooooooooo(o))
     60: (oo(o)((o)))
  12288: (oooooooooooo(o))
    832: (oooooo(o(o)))
    144: (oooo(o)(o))
    712: (ooo(ooo(o)))

Position of first appearance of n in A206487.
The sorted version is A358507.
A000081 counts rooted trees, ordered A000108.
A214577 and A358377 rank trees with no permutations.
Cf. A001263, A032027, A061775, A127301, A196050, A358378, A358506, A358521, A358522.

primeMS[n_]:=If[n===1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]]
MGTree[n_Integer]:=If[n===1,{},MGTree/@primeMS[n]]
treeperms[t_]:=Times @@ Cases[t,b:{}:>Length[Permutations[b]],{0,Infinity}];
uv=Table[treeperms[MGTree[n]],{n,100000}];
Table[Position[uv,k][[1,1]],{k,Min@@Complement[Range[Max@@uv],uv]-1}]

A243497 A243496 sorted into ascending order, with duplicates removed.

Original entry on oeis.org

1, 2, 3, 4, 5, 7, 8, 9, 11, 16, 17, 19, 23, 25, 27, 31, 32, 49, 53, 59, 64, 67, 81, 83, 97, 103, 121, 125, 127, 128, 131, 169, 227, 241, 243, 256, 277, 289, 311, 331, 343, 361, 419, 431, 509, 512, 529, 563, 661, 691, 709, 719, 739, 841, 961, 1009, 1024, 1433, 1523, 1619, 1681, 1787, 1849, 1879, 2063

Offset: 0

Antti Karttunen, Jun 07 2014

nonn

Matula-codes for trees which are almost "uniform", but which allow cases like 169, 841, 1009, 1681, 1849, ... where there is a special relation between prime index and the exponent. (Cf. the comments at A243496).
Differs from A214577 for the first time at n=31, where A214577(31)=227, while here we have 169 at that position, because it corresponds exactly to that "dual" case mentioned in A057546, in excess to those mentioned in A003238. Note that 169 = 13*13 = p_{2*3}^2.
a(0) = 1 stands for the empty tree.

Cf. A214577 (a subsequence), A209638, A243494.

A298126 Matula-Goebel numbers of rooted trees in which all outdegrees are even.

Original entry on oeis.org

1, 4, 14, 16, 49, 56, 64, 86, 106, 196, 224, 256, 301, 344, 371, 424, 454, 526, 622, 686, 784, 886, 896, 1024, 1154, 1204, 1376, 1484, 1589, 1696, 1816, 1841, 1849, 2104, 2177, 2279, 2386, 2401, 2488, 2744, 2809, 2846, 3101, 3136, 3238, 3544, 3584, 3986, 4039

Offset: 1

Gus Wiseman, Jan 13 2018

nonn

			Sequence of trees begins:
1   o
4   (oo)
14  (o(oo))
16  (oooo)
49  ((oo)(oo))
56  (ooo(oo))
64  (oooooo)
86  (o(o(oo)))
106 (o(oooo))
196 (oo(oo)(oo))
224 (ooooo(oo))
256 (oooooooo)
301 ((oo)(o(oo)))
344 (ooo(o(oo)))
371 ((oo)(oooo))
424 (ooo(oooo))
454 (o((oo)(oo)))
526 (o(ooo(oo)))
622 (o(oooooo))
686 (o(oo)(oo)(oo))
784 (oooo(oo)(oo))
886 (o(o(o(oo))))
896 (ooooooo(oo))

Index entries for sequences related to Matula-Goebel numbers

Cf. A000081, A001190, A007097, A026424, A028260, A061775, A111299, A214577, A245824, A276625, A277098, A290760, A291441, A291442, A291636, A295461, A297571, A298118, A298120.

primeMS[n_]:=If[n===1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
etQ[n_]:=Or[n===1,With[{m=primeMS[n]},EvenQ@Length@m&&And@@etQ/@m]];
Select[Range[10000],etQ]

A298303 Matula-Goebel numbers of rooted trees with thinning limbs.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 8, 9, 10, 11, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 26, 27, 28, 30, 31, 32, 33, 35, 36, 39, 40, 42, 44, 45, 46, 48, 49, 50, 52, 54, 55, 56, 58, 60, 62, 63, 64, 65, 66, 69, 70, 72, 75, 76, 77, 78, 80, 81, 84, 86, 87, 88, 90, 91, 92, 93, 94

Offset: 1

Gus Wiseman, Jan 16 2018

nonn

An unlabeled rooted tree has thinning limbs if its outdegrees are weakly decreasing from root to leaves.

Cf. A000081, A007097, A061775, A111299, A124343, A124346, A214577, A276625, A290760, A291636, A298126, A298120, A298304, A298305.

MGtree[n_]:=If[n===1,{},MGtree/@Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
thinQ[t_]:=And@@Cases[t,b_List:>Length[b]>=Max@@Length/@b,{0,Infinity}];
Select[Range[200],thinQ[MGtree[#]]&]

A298534 Matula-Goebel numbers of rooted trees such that every branch of the root has the same number of leaves.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 15, 16, 17, 18, 19, 20, 22, 23, 24, 25, 27, 29, 30, 31, 32, 33, 36, 37, 40, 41, 43, 44, 45, 47, 48, 49, 50, 53, 54, 55, 59, 60, 61, 62, 64, 66, 67, 71, 72, 73, 75, 79, 80, 81, 83, 88, 89, 90, 91, 93, 96, 97, 99, 100

Offset: 1

Gus Wiseman, Jan 20 2018

nonn

			Sequence of trees begins:
1  o
2  (o)
3  ((o))
4  (oo)
5  (((o)))
6  (o(o))
7  ((oo))
8  (ooo)
9  ((o)(o))
10 (o((o)))
11 ((((o))))
12 (oo(o))
13 ((o(o)))
15 ((o)((o)))
16 (oooo)
17 (((oo)))
18 (o(o)(o))
19 ((ooo))
20 (oo((o)))
22 (o(((o))))
23 (((o)(o)))
24 (ooo(o))
25 (((o))((o)))
27 ((o)(o)(o))
29 ((o((o))))
30 (o(o)((o)))

Cf. A000081, A007097, A061775, A111299, A214577, A276625, A290760, A290822, A291442, A298533, A298536.

nn=2000;
primeMS[n_]:=If[n===1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
leafcount[n_]:=If[n===1,1,With[{m=primeMS[n]},If[Length[m]===1,leafcount[First[m]],Total[leafcount/@m]]]];
Select[Range[nn],SameQ@@leafcount/@primeMS[#]&]

cp's OEIS Frontend

A298536 Matula-Goebel numbers of rooted trees such that every branch of the root has a different number of leaves.

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A317099 Number of series-reduced planted achiral trees whose leaves span an initial interval of positive integers appearing with multiplicities an integer partition of n.

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A317853 a(1) = 1; a(n > 1) = Sum_{0 < k < n} (-1)^(n - k - 1) a(n - k) Sum_{d|k} a(d).

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A331991 Number of semi-lone-child-avoiding achiral rooted trees with n vertices.

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A331992 Matula-Goebel numbers of semi-lone-child-avoiding achiral rooted trees.

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Mathematica

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A358508 Least Matula-Goebel number of a tree with exactly n permutations.

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A243497 A243496 sorted into ascending order, with duplicates removed.

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A298126 Matula-Goebel numbers of rooted trees in which all outdegrees are even.

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Mathematica

A298303 Matula-Goebel numbers of rooted trees with thinning limbs.

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A298534 Matula-Goebel numbers of rooted trees such that every branch of the root has the same number of leaves.