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A280089
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a(n) = 4 * n^3 - 3 * n + 1.
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3
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1, 2, 27, 100, 245, 486, 847, 1352, 2025, 2890, 3971, 5292, 6877, 8750, 10935, 13456, 16337, 19602, 23275, 27380, 31941, 36982, 42527, 48600, 55225, 62426, 70227, 78652, 87725, 97470, 107911, 119072, 130977, 143650, 157115, 171396, 186517, 202502, 219375
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n) = (2n - 1)^2 * (n + 1).
Prod_{k >= 1}(A033430(k) / a(k)) = Pi.
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MATHEMATICA
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PROG
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(PARI) a(n) = (2*n-1)^2 * (n+1).
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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