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A358456
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Number of recursively bi-anti-transitive ordered rooted trees with n nodes.
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5
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1, 1, 2, 3, 7, 17, 47, 117, 321, 895, 2556, 7331, 21435, 63116, 187530
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OFFSET
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1,3
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COMMENTS
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We define an unlabeled ordered rooted tree to be recursively bi-anti-transitive if there are no two branches of the same node such that one is a branch of the other.
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LINKS
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EXAMPLE
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The a(1) = 1 through a(6) = 17 trees:
o (o) (oo) (ooo) (oooo) (ooooo)
((o)) ((oo)) ((ooo)) ((oooo))
(((o))) (((o))o) (((o))oo)
(((oo))) (((oo))o)
((o)(o)) (((ooo)))
(o((o))) ((o)(oo))
((((o)))) ((oo)(o))
(o((o))o)
(o((oo)))
(oo((o)))
((((o)))o)
((((o))o))
((((oo))))
(((o)(o)))
((o((o))))
(o(((o))))
(((((o)))))
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MATHEMATICA
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aot[n_]:=If[n==1, {{}}, Join@@Table[Tuples[aot/@c], {c, Join@@Permutations/@IntegerPartitions[n-1]}]];
Table[Length[Select[aot[n], FreeQ[#, {___, x_, ___, {___, x_, ___}, ___}|{___, {___, x_, ___}, ___, x_, ___}]&]], {n, 10}]
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CROSSREFS
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A306844 counts anti-transitive rooted trees.
Cf. A318185, A324695, A324751, A324756, A324758, A324764, A324767, A324768, A324838, A324840, A324844.
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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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