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A222463
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a(n) = n*5/gcd(n*5,n+5), n >= 5.
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2
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5, 30, 35, 40, 45, 10, 55, 60, 65, 70, 15, 80, 85, 90, 95, 4, 105, 110, 115, 120, 25, 130, 135, 140, 145, 30, 155, 160, 165, 170, 35, 180, 185, 190, 195, 40, 205, 210, 215, 220, 9, 230, 235, 240, 245, 50, 255, 260, 265, 270, 55, 280, 285, 290, 295, 60
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OFFSET
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5,1
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COMMENTS
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This is the fifth column (m=5) of the triangle A221918.
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LINKS
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Index entries for linear recurrences with constant coefficients, signature (0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,-1).
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FORMULA
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a(n) = A221918(n,5) = numerator(n*5/(n+5)) = n*5/gcd(n*5,n+5) = n*5/gcd(25,n+5), n >= 5.
Sum_{k=5..n} a(k) ~ (521/250) * n^2. - Amiram Eldar, Oct 09 2023
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EXAMPLE
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a(10) = numerator(50/15) = numerator(10/3) = 10 = 50/gcd(50,15)= 50/5 = 50/gcd(25,15).
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MATHEMATICA
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Table[(5n)/GCD[5n, n +5], {n, 5, 60}] (* Harvey P. Dale, Nov 06 2020 *)
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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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