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A109046
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a(n) = lcm(n, 5).
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4
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0, 5, 10, 15, 20, 5, 30, 35, 40, 45, 10, 55, 60, 65, 70, 15, 80, 85, 90, 95, 20, 105, 110, 115, 120, 25, 130, 135, 140, 145, 30, 155, 160, 165, 170, 35, 180, 185, 190, 195, 40, 205, 210, 215, 220, 45, 230, 235, 240, 245, 50, 255, 260, 265, 270, 55, 280, 285, 290
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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 (0,0,0,0,2,0,0,0,0,-1).
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FORMULA
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G.f.: 5*x*(x^4+x^3+3*x^2+x+1)*(x^4+x^3-x^2+x+1) / ( (x-1)^2*(x^4+x^3+x^2+x+1)^2 ). - R. J. Mathar, Apr 18 2011
Sum_{k=1..n} a(k) ~ (21/10) * n^2. - Amiram Eldar, Nov 26 2022
Sum_{n>=1} (-1)^(n+1)/a(n) = 9*log(2)/25. - Amiram Eldar, Sep 08 2023
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MATHEMATICA
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a[n_] := LCM[n, 5]; Array[a, 60, 0] (* Amiram Eldar, Nov 26 2022 *)
LinearRecurrence[{0, 0, 0, 0, 2, 0, 0, 0, 0, -1}, {0, 5, 10, 15, 20, 5, 30, 35, 40, 45}, 60] (* Harvey P. Dale, Oct 08 2023 *)
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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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