Lets $\phi(n)$ is Euler's phi function. Let's define error term 
$$
d(n) = {E(n) \over n} = {1 \over n} \left(\sum\_{i\le n}\phi(i) - {3 n^2 \over \pi^2}\right)
$$


Is it known that asymptotic of mean (and median) of the first N values $d(n)$ is equal to 3/\pi^2?


$$
\lim\_{N\to\infty} {\sum\_{n=1}^N d(n) \over N} = 3/\pi^2
$$


I can't extract this fact from the papers [Oscillations of the remainder term related to the Euler totient function](http://www.sciencedirect.com/science/article/pii/S0022314X10001873) and [The Existence of a Distribution Function for an Error Term Related to the Euler Function](https://users.renyi.hu/~p_erdos/1955-16.pdf).


[Mathematica code](https://i.stack.imgur.com/d1NKs.jpg)


Update: bug fixed - the limit is not 1 but 3/π^2, as noticed below by GH from MO.



Mean and median of error term of average Euler-phi function
The limit is not $1$ but $3/\pi^2$ (in agreement with [your Mathematica code](https://i.stack.imgur.com/d1NKs.jpg)). To see this, let us use the following result of Pillai and Chowla ([On the error terms in some asymptotic formulae in the theory of numbers, (I)](https://doi.org/10.1112/jlms/s1-5.2.95), J. London Math. Soc. 5 (1930), 95-101):
$$S(x):=\sum\_{n\leq x}E(n)=\left(\frac{3}{2\pi^2}+o(1)\right)x^2.$$
We infer
\begin{align\*}\sum\_{n=1}^N\frac{E(n)}{n}&=\int\_{1-}^N\frac{dS(x)}{x}=\frac{S(N)}{N}+\int\_1^N\frac{S(x)}{x^2}\,dx\\[8pt]
&=\left(\frac{3}{2\pi^2}+o(1)\right)N+\int\_1^N\left(\frac{3}{2\pi^2}+o(1)\right)dx\\[8pt]
&=\left(\frac{3}{\pi^2}+o(1)\right)N.\end{align\*}


