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A190120
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a(n) = Sum_{k=1..n} lcm(k,k')/gcd(k,k'), where n' is arithmetic derivative of n.
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2
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0, 2, 5, 6, 11, 41, 48, 54, 60, 130, 141, 153, 166, 292, 412, 414, 431, 473, 492, 522, 732, 1018, 1041, 1107, 1117, 1507, 1508, 1564, 1593, 2523, 2554, 2564, 3026, 3672, 4092, 4107, 4144, 4942, 5566, 5736, 5777, 7499, 7542, 7674, 7869, 9019, 9066, 9087, 9101, 9191
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OFFSET
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1,2
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COMMENTS
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Use lcm(1,0)=0 and gcd(1,0)=1.
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LINKS
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EXAMPLE
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lcm(1,1')/gcd(1,1')+lcm(2,2')/gcd(2,2')+lcm(3,3')/gcd(3,3')=0+2/1+3/1=5 ->a(3)=5.
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MAPLE
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der:=n->n*add(op(2, p)/op(1, p), p=ifactors(n)[2]):
seq(add(lcm(der(i), i)/gcd(der(i), i), i=1..n), n=1..50);
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MATHEMATICA
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A003415[n_]:= If[Abs@n < 2, 0, n Total[#2/#1 & @@@FactorInteger[Abs@n]]];
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PROG
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(PARI) {A003145(n, f)=sum(i=1, #f=factor(n)~, n/f[1, i]*f[2, i])};
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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