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A240877
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Sum of the denominators of the Farey series of order n (A006843).
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10
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1, 2, 4, 10, 18, 38, 50, 92, 124, 178, 218, 328, 376, 532, 616, 736, 864, 1136, 1244, 1586, 1746, 1998, 2218, 2724, 2916, 3416, 3728, 4214, 4550, 5362, 5602, 6532, 7044, 7704, 8248, 9088, 9520, 10852, 11536, 12472, 13112, 14752, 15256, 17062, 17942, 19022, 20034, 22196, 22964, 25022, 26022
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OFFSET
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0,2
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COMMENTS
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All terms except a(0) are even.
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LINKS
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FORMULA
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MATHEMATICA
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Farey[n_] := Union[ Flatten[ Join[{0}, Table[a/b, {b, n}, {a, b}]]]]; Table[ Total[ Denominator[ Farey[ n]]], {n, 0, 50}]
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PROG
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(PARI) first(n)=my(s=1, v=vector(n+1)); v[1]=1; forfactored(k=1, n, v[k[1]+1]=s+=k[1]*eulerphi(k)); v \\ Charles R Greathouse IV, Dec 27 2017
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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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