I am studying for a test and I was able to find the cofinality 3 of the 4 ones given, but am having a lot of trouble with the 4th. the 3 first ones are:
- $\newcommand{\cf}{\operatorname{cf}}\cf(\aleph_\omega)=\omega$
- $\cf(\aleph_{\omega^2})=\omega$
- $\cf(\omega_1)=\omega_1$
I do not know how to calcuate $\cf(\aleph_{\omega\cdot9 + 3})$. I am very tempted to say it is simply $\omega$.
Thank you.