Maass forms of levels 1 to 15 with $0 \leq R\leq 15$
The horizontal axis is the spectral parameter $R$ with the Laplace eigenvalue satisying $\lambda=1/4+R^2$. The vertical axis is the level $N$. Each point corresponds to a Maass form of weight 0 and trivial character on $\Gamma_0(N)$ with the color showing whether the symmetry is even or odd. For $N>100$ there are only results for prime level.
In the plot below each dot is linked to the homepage of the corresponding Maass forms.