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A109051
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a(n) = lcm(n,10).
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4
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0, 10, 10, 30, 20, 10, 30, 70, 40, 90, 10, 110, 60, 130, 70, 30, 80, 170, 90, 190, 20, 210, 110, 230, 120, 50, 130, 270, 140, 290, 30, 310, 160, 330, 170, 70, 180, 370, 190, 390, 40, 410, 210, 430, 220, 90, 230, 470, 240, 490, 50, 510, 260, 530, 270, 110, 280
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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 (0,0,0,0,0,0,0,0,0,2,0,0,0,0,0,0,0,0,0,-1).
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FORMULA
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a(n) = n*10/gcd(n, 10).
G.f.: 10*x*(1 +x +3*x^2 +2*x^3 +x^4 +3*x^5 +7*x^6 +4*x^7 +9*x^8 +x^9 +9*x^10 +4*x^11 +7*x^12 +3*x^13 +x^14 +2*x^15 +3*x^16 +x^17 +x^18)/(1 -x^10)^2. - Robert Israel, Feb 23 2016
Sum_{k=1..n} a(k) ~ (63/20) * n^2. - Amiram Eldar, Nov 26 2022
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MAPLE
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q:= [seq(10/igcd(i, 10), i=1..10)]:
[0, seq(seq((10*i+j)*q[j], j=1..10), i=0..10)]; # Robert Israel, Feb 23 2016
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MATHEMATICA
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a[n_] := LCM[n, 10]; Array[a, 60, 0] (* Amiram Eldar, Nov 26 2022 *)
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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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