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
a(n) ~ c * n^3, where c = 2/Pi^2 (A185197). - Amiram Eldar, Dec 01 2023
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
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Apr 13 2014
STATUS
approved