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A028494
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a(n) = -(1/2)*(n+2)*(n^2 - 6*n - 1).
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1
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1, 9, 18, 25, 27, 21, 4, -27, -75, -143, -234, -351, -497, -675, -888, -1139, -1431, -1767, -2150, -2583, -3069, -3611, -4212, -4875, -5603, -6399, -7266, -8207, -9225, -10323, -11504, -12771, -14127, -15575, -17118, -18759, -20501, -22347
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OFFSET
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0,2
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LINKS
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MATHEMATICA
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Table[-(1/2)(n+2)(n^2-6n-1), {n, 0, 40}] (* or *) LinearRecurrence[{4, -6, 4, -1}, {1, 9, 18, 25}, 40] (* Harvey P. Dale, Sep 08 2018 *)
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PROG
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CROSSREFS
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KEYWORD
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sign,easy
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AUTHOR
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STATUS
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approved
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