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A027694
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a(n) = n^2 + n + 9.
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5
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9, 11, 15, 21, 29, 39, 51, 65, 81, 99, 119, 141, 165, 191, 219, 249, 281, 315, 351, 389, 429, 471, 515, 561, 609, 659, 711, 765, 821, 879, 939, 1001, 1065, 1131, 1199, 1269, 1341, 1415, 1491, 1569, 1649, 1731, 1815, 1901, 1989, 2079, 2171
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refs;
listen;
history;
text;
internal format)
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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.: (-9 + 16*x - 9*x^2) / (x-1)^3. - R. J. Mathar, Feb 07 2011
Sum_{n>=0} 1/a(n) = Pi*tanh(Pi*sqrt(35)/2)/sqrt(35). - Amiram Eldar, Jan 17 2021
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MAPLE
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with (combinat):seq(fibonacci(3, n)+n+8, n=0..46); # Zerinvary Lajos, Jun 07 2008
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MATHEMATICA
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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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