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A240877 Sum of the denominators of the Farey series of order n (A006843). 10
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

All terms except a(0) are even.

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 0..10000

FORMULA

a(n) = 1 + Sum_{k=1..n} k*A000010(k). - Isaac Saffold, Dec 03 2017

a(n) = 1 + A011755(n). - Michel Marcus, Dec 23 2017

MATHEMATICA

Farey[n_] := Union[ Flatten[ Join[{0}, Table[a/b, {b, n}, {a, b}]]]]; Table[ Total[ Denominator[ Farey[ n]]], {n, 0, 50}]

PROG

(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

CROSSREFS

Cf. A000010, A006842, A006843, A011755, A213544.

Sequence in context: A279359 A242261 A189892 * A218008 A197049 A104723

Adjacent sequences:  A240874 A240875 A240876 * A240878 A240879 A240880

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Apr 13 2014

STATUS

approved

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Last modified February 20 12:02 EST 2018. Contains 299387 sequences. (Running on oeis4.)