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A085919
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Number of ways a loop can cross three roads meeting in a Y n times.
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1
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3, 0, 3, 1, 9, 6, 45, 42, 279, 320, 1977, 2610, 15306, 22404, 126300, 200158, 1093515, 1846314, 9830547, 17481864
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OFFSET
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0,1
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COMMENTS
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The Mercedes-Benz problem: closed meanders crossing a Y.
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LINKS
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EXAMPLE
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With three crossings the loop must cut each road exactly once, so a(3) = 1.
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CROSSREFS
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Similar to A078104, but without the constraint of touching the (-, -) quadrant.
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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