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A367118
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Place n points in general position on each side of an equilateral triangle, and join every pair of the 3*n+3 boundary points by a chord; sequence gives number of regions in the resulting planar graph.
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8
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1, 13, 82, 307, 841, 1891, 3718, 6637, 11017, 17281, 25906, 37423, 52417, 71527, 95446, 124921, 160753, 203797, 254962, 315211, 385561, 467083, 560902, 668197, 790201, 928201, 1083538, 1257607, 1451857, 1667791, 1906966, 2170993, 2461537, 2780317, 3129106, 3509731, 3924073, 4374067
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OFFSET
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0,2
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COMMENTS
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"In general position" implies that the internal lines (or chords) only have simple intersections. There is no interior point where three or more chords meet.
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LINKS
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FORMULA
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Conjecture: a(n) = (1/4)*(9*n^4 + 12*n^3 + 15*n^2 + 12*n + 4).
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CROSSREFS
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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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