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A333080
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Number of fixed Tangles of size n.
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2
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1, 2, 6, 22, 88, 372, 1626, 7292, 33309, 154374, 723740, 3425124, 16336747, 78437858
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OFFSET
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0,2
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COMMENTS
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a(n) is the number of fixed Tangles (smooth simple closed curves piecewise-defined by quadrants of circles) which have a dual graph containing n edges, or equivalently, enclose an area of (4*n + Pi)*r^2, where 1/r is the curvature. By 'fixed', we mean that we do not allow rotations or reflections.
Dual graphs of Tangles are polyedges (A096267), but the only chordless cycles allowed are squares, e.g., this is *not* the dual graph of a Tangle:
o-o-o
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o-o-o
but this is:
o-o-o
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o-o-o
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LINKS
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CROSSREFS
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Dual graphs of Tangles which are trees are bond trees on the square lattice (A308409), free Tangles (A333233).
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KEYWORD
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nonn,hard,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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