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A047928
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a(n) = n*(n-1)^2*(n-2).
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17
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0, 12, 72, 240, 600, 1260, 2352, 4032, 6480, 9900, 14520, 20592, 28392, 38220, 50400, 65280, 83232, 104652, 129960, 159600, 194040, 233772, 279312, 331200, 390000, 456300, 530712, 613872, 706440, 809100, 922560, 1047552, 1184832
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OFFSET
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2,2
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LINKS
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FORMULA
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a(n) = floor((n-1)^6/((n-1)^2+1)). - Gary Detlefs, Feb 11 2010
Sum_{n>=3} 1/a(n) = 7/4 - Pi^2/6.
Sum_{n>=3} (-1)^(n+1)/a(n) = Pi^2/12 - 3/4. (End)
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MAPLE
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seq(floor(n^6/(n^2+1)), n=1..25); # Gary Detlefs, Feb 11 2010
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MATHEMATICA
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LinearRecurrence[{5, -10, 10, -5, 1}, {0, 12, 72, 240, 600}, 40] (* or *) CoefficientList[Series[-((12 x (1+x))/(-1+x)^5), {x, 0, 40}], x] (* Harvey P. Dale, Jul 31 2021 *)
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PROG
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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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