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A358458 Numbers k such that the k-th standard ordered rooted tree is weakly transitive (counted by A358454). 2

%I #5 Nov 18 2022 23:36:40

%S 1,2,4,6,7,8,12,14,15,16,18,22,23,24,25,27,28,30,31,32,36,38,39,42,44,

%T 45,46,47,48,50,51,53,54,55,56,57,59,60,62,63,64,70,71,72,76,78,79,82,

%U 84,86,87,88,89,90,91,92,93,94,95,96,99,100,102,103,105

%N Numbers k such that the k-th standard ordered rooted tree is weakly transitive (counted by A358454).

%C We define an unlabeled ordered rooted tree to be weakly transitive if every branch of a branch of the root is itself a branch of the root.

%C We define the n-th standard ordered rooted tree to be obtained by taking the (n-1)-th composition in standard order (graded reverse-lexicographic, A066099) as root and replacing each part with its own standard ordered rooted tree. This ranking is an ordered variation of Matula-Goebel numbers, giving a bijective correspondence between positive integers and unlabeled ordered rooted trees.

%H Gus Wiseman, <a href="https://docs.google.com/document/d/e/2PACX-1vTCPiJVFUXN8IqfLlCXkgP15yrGWeRhFS4ozST5oA4Bl2PYS-XTA3sGsAEXvwW-B0ealpD8qnoxFqN3/pub">Statistics, classes, and transformations of standard compositions</a>

%e The terms together with their corresponding ordered trees begin:

%e 1: o

%e 2: (o)

%e 4: (oo)

%e 6: ((o)o)

%e 7: (o(o))

%e 8: (ooo)

%e 12: ((o)oo)

%e 14: (o(o)o)

%e 15: (oo(o))

%e 16: (oooo)

%e 18: ((oo)o)

%e 22: ((o)(o)o)

%e 23: ((o)o(o))

%e 24: ((o)ooo)

%t stc[n_]:=Differences[Prepend[Join @@ Position[Reverse[IntegerDigits[n,2]],1],0]]//Reverse;

%t srt[n_]:=If[n==1,{},srt/@stc[n-1]];

%t Select[Range[100],Complement[Union@@srt[#],srt[#]]=={}&]

%Y The unordered version is A290822, counted by A290689.

%Y These trees are counted by A358454.

%Y The directed version is A358457, counted by A358453.

%Y A000108 counts ordered rooted trees, unordered A000081.

%Y A306844 counts anti-transitive rooted trees.

%Y A324766 ranks recursively anti-transitive rooted trees, counted by A324765.

%Y A358455 counts recursively anti-transitive ordered rooted trees.

%Y Cf. A004249, A032027, A318185, A324695, A324758, A324766, A324840, A358373-A358377, A358456.

%K nonn

%O 1,2

%A _Gus Wiseman_, Nov 18 2022

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Last modified March 29 11:14 EDT 2024. Contains 371278 sequences. (Running on oeis4.)