@article {FerrariSillari2023, title = {On the Minimal Number of Solutions of the Equation φ(n+k)=Mφ(n), M=1,2}, journal = {Journal of Integer Sequences}, volume = {26}, year = {2023}, month = {01/2023}, type = {Article}, abstract = {We fix a positive integer $k$ and look for solutions $n \in \mathbb{N}$ of the equations $\phi(n + k) = \phi(n)$ and $φ(n + k) = 2 φ(n)$. For $k \le 12 \cdot 10^{100}$, we prove that Fermat primes can be used to build five solutions for the first equation when $k$ is even, and five for the second one when $k$ is odd. Furthermore, for $k \le 4 \cdot 10^{58}$, we show that for the second equation there are at least three solutions when $k$ is even. Our work increases the previously known minimal number of solutions for both equations.}, keywords = {Euler{\textquoteright}s phi function}, issn = {1530-7638}, url = {https://cs.uwaterloo.ca/journals/JIS/VOL26/Sillari/sillari3.html}, author = {Matteo Ferrari and Lorenzo Sillari} } @article {ST21, title = {Doulbeault and J-invariant Cohomologies on Almost Complex Manifolds}, journal = {Complex Analysis and Operator Theory}, volume = {15}, year = {2021}, month = {09/2021}, type = {Article}, abstract = {In this paper we relate the cohomology of $J$-invariant forms to the Dolbeault cohomology of an almost complex manifold. We find necessary and sufficient condition for the inclusion of the former into the latter to be true up to isomorphism. We also extend some results obtained by J. Cirici and S. O. Wilson about the computation of the left-invariant cohomology of nilmanifolds to the setting of solvmanifolds. Several examples are given.}, keywords = {Almost Complex Manifolds, Cohomology of Lie Algebra, Compact four-manifold, Dolbeault Cohomology, Fr{\"o}licher Spectral Sequence, Solvmanifold}, doi = {https://doi.org/10.1007/s11785-021-01156-w}, url = {https://link.springer.com/article/10.1007/s11785-021-01156-w}, author = {Lorenzo Sillari and Adriano Tomassini} }