A277996 -id:A277996 - cp's OEIS frontend

A317659 Regular triangle where T(n,k) is the number of distinct free pure symmetric multifunctions (with empty expressions allowed) with one atom, n positions, and k leaves.

1, 1, 0, 1, 1, 0, 1, 3, 1, 0, 1, 6, 5, 1, 0, 1, 10, 17, 7, 1, 0, 1, 15, 43, 33, 9, 1, 0, 1, 21, 92, 118, 55, 11, 1, 0, 1, 28, 174, 341, 252, 82, 13, 1, 0, 1, 36, 302, 845, 935, 463, 115, 15, 1, 0, 1, 45, 490, 1864, 2921, 2103, 769, 153, 17, 1, 0, 1, 55, 755

Offset: 1

Gus Wiseman, Aug 03 2018

			The T(5,3) = 5 expressions are o[o[o]], o[o,o[]], o[][o,o], o[o][o], o[o,o][].
Triangle begins:
    1
    1    0
    1    1    0
    1    3    1    0
    1    6    5    1    0
    1   10   17    7    1    0
    1   15   43   33    9    1    0
    1   21   92  118   55   11    1    0
    1   28  174  341  252   82   13    1    0
    1   36  302  845  935  463  115   15    1    0
    1   45  490 1864 2921 2103  769  153   17    1    0
    1   55  755 3755 7981 8012 4145 1187  197   19    1    0

Mathematica Reference, Orderless

Cf. A001003, A052893, A053492, A255906, A277996, A279944, A280000.

Cf. A317652, A317653, A317654, A317655, A317656, A317676.

maxUsing[n_]:=If[n==1,{"o"},Join@@Cases[Table[PR[k,n-k-1],{k,n-1}],PR[h_,g_]:>Join@@Table[Apply@@@Tuples[{maxUsing[h],Union[Sort/@Tuples[maxUsing/@p]]}],{p,IntegerPartitions[g]}]]];
Table[Length[Select[maxUsing[n],Length[Position[#,"o"]]==k&]],{n,12},{k,n}]

A318151 e-numbers of unlabeled rooted trees with empty leaves o[] allowed. A number n is in the sequence iff n = 2^(prime(y_1) * ... * prime(y_k)) for some k >= 0 and y_1, ..., y_k already in the sequence.

Original entry on oeis.org

1, 2, 4, 8, 16, 64, 128, 256, 512, 4096, 16384, 65536, 262144, 524288, 2097152, 16777216, 134217728, 268435456, 4294967296, 68719476736, 274877906944, 4398046511104, 281474976710656, 562949953421312, 9007199254740992, 18014398509481984, 72057594037927936

Offset: 1

Gus Wiseman, Aug 19 2018

nonn

If n = 1 let e(n) be the leaf symbol "o". Given a positive integer n > 1 we construct a unique orderless expression e(n) (as can be represented in functional programming languages such as Mathematica) with one atom by expressing n as a power of a number that is not a perfect power to a product of prime numbers: n = rad(x)^(prime(y_1) * ... * prime(y_k)) where rad = A007916. Then e(n) = e(x)[e(y_1), ..., e(y_k)]. For example, e(21025) = o[o[o]][o] because 21025 = rad(rad(1)^prime(rad(1)^prime(1)))^prime(1). The sequence consists of all numbers n such that e(n) contains no subexpressions in heads f[x_1, ..., x_k][y_1, ..., y_k] where k,j >= 0.

A subsequence of A000079.
Cf. A000081, A007916, A029856, A052409, A052410, A277576, A277996, A280000.
Cf. A317658, A316112, A317056, A317765, A317994, A318149, A318150, A318152, A318153.

A322752 Number of "funny trees" on n nodes.

Original entry on oeis.org

0, 2, 3, 9, 30, 110, 423, 1706, 7085, 30186, 131071, 578194, 2583377, 11667874, 53180604, 244301512, 1129947243, 5257592237, 24592945975, 115578827200, 545478791124, 2584216074295, 12285025045259, 58584860422121, 280181867792399, 1343499543045511, 6457845289959966

Offset: 0

N. J. A. Sloane, Dec 25 2018

nonn

For precise definition see Example 15.3.7 of Bona (2015).

The trees considered here have nodes of two types: black and white. The child nodes of black nodes are unordered and can be either black or white. The child nodes of white nodes are linearly ordered and must be black. - Andrew Howroyd, Feb 06 2025

Miklos Bona, editor, Handbook of Enumerative Combinatorics, CRC Press, 2015, page 1002.

Andrew Howroyd, Table of n, a(n) for n = 0..500
N. J. A. Sloane, Annotated scan of page 1001 of Bona (2015).
N. J. A. Sloane, Annotated scan of page 1002 of Bona (2015).

Cf. A277996.

EulerT(v)={Vec(exp(x*Ser(dirmul(v,vector(#v,n,1/n))))-1, -#v)}
seq(n)={my(w=O(x),b=O(x)); for(n=1, n, w=x/(1-b); b=x*(1 + x*Ser(EulerT(Vec(b+w))))); Vec(b+w, -n-1)} \\ Andrew Howroyd, Feb 06 2025

Offset corrected and a(7) onwards from Andrew Howroyd, Feb 06 2025

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A317659 Regular triangle where T(n,k) is the number of distinct free pure symmetric multifunctions (with empty expressions allowed) with one atom, n positions, and k leaves.

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A318151 e-numbers of unlabeled rooted trees with empty leaves o[] allowed. A number n is in the sequence iff n = 2^(prime(y_1) * ... * prime(y_k)) for some k >= 0 and y_1, ..., y_k already in the sequence.

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A322752 Number of "funny trees" on n nodes.

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