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A109050
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a(n) = lcm(n, 9).
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3
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0, 9, 18, 9, 36, 45, 18, 63, 72, 9, 90, 99, 36, 117, 126, 45, 144, 153, 18, 171, 180, 63, 198, 207, 72, 225, 234, 27, 252, 261, 90, 279, 288, 99, 306, 315, 36, 333, 342, 117, 360, 369, 126, 387, 396, 45, 414, 423, 144, 441, 450, 153, 468, 477, 54, 495, 504
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OFFSET
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0,2
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LINKS
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Index entries for linear recurrences with constant coefficients, signature (0,0,0,0,0,0,0,0,2,0,0,0,0,0,0,0, 0,-1).
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FORMULA
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a(n) = n*9/gcd(n, 9).
Sum_{k=1..n} a(k) ~ (61/18) * n^2. - Amiram Eldar, Nov 26 2022
Sum_{n>=1} (-1)^(n+1)/a(n) = 7*log(2)/27. - Amiram Eldar, Sep 08 2023
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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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