Are there any formulas due to Ramanujan that have still not been proved—or disproved?

If so, what are they?

I believe this conjecture is due to Ramanujan and still open: if $x$ is a real number and $2^x$ and $3^x$ are both integers then $x$ is an integer. There may be other open conjectures due Ramanujan. However, right now I'm mainly interested in *formulas*, i.e. identities, that he wrote down.

whichproblem has a positive answer? $\endgroup$ – Gerry Myerson Nov 21 '20 at 23:017more comments