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A027690
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a(n) = n^2 + n + 5.
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10
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5, 7, 11, 17, 25, 35, 47, 61, 77, 95, 115, 137, 161, 187, 215, 245, 277, 311, 347, 385, 425, 467, 511, 557, 605, 655, 707, 761, 817, 875, 935, 997, 1061, 1127, 1195, 1265, 1337, 1411, 1487, 1565, 1645, 1727, 1811, 1897, 1985, 2075, 2167, 2261
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listen;
history;
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OFFSET
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0,1
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LINKS
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FORMULA
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G.f.: (5 - 8*x + 5*x^2)/(1 - x)^3.
Sum_{n>=0} 1/a(n) = Pi*tanh(sqrt(19)*Pi/2)/sqrt(19) = 0.720729156259... (End)
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MAPLE
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with (combinat):seq(fibonacci(3, n)+n+4, n=0..47); # Zerinvary Lajos, Jun 07 2008
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MATHEMATICA
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Table[n^2 + n + 5, {n, 0, 100}] (* T. D. Noe, Oct 29 2009 *)
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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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EXTENSIONS
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STATUS
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approved
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