Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
$H^*(\mathbb{CP}^{\infty},k) = k[x]$ has basis $\{x^i : i \geq 0\}$. Of course, every other nontrivial computation of (co)homology groups fits in here.
