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1, 127, 4054, 37210, 134325, 776241, 1313848, 5536128, 7280823, 28243653, 32246894, 74873810
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OFFSET
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1,2
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COMMENTS
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Partial sums of number of equilateral triangles whose vertices (whether connected by lines or not) lie at intersection points resulting from drawing lines connecting every pair of vertices of a regular 3n-gon (and extending beyond the polygon). The subsequence of primes in this partial sum begins: 127, x.
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LINKS
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FORMULA
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EXAMPLE
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a(4) = 1 + 126 + 3927 + 33156 = 37210 = 2 * 5 * 61^2.
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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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