[ndsipa_pomu]

The "to this day" is in my opinion unnecessary - you could phrase it as "no one has proved it mathematically".

Alternatively, "it has yet to be proved mathematically".

[jay_gridbach]

Thank you. Just removed "to this day".

[jey]

Btw despite the helpful pedanticism[1] of HN, I think your English is impeccable and idiomatically natural for someone who has probably not spent much time in immersive spoken English environments.

1. pedantry

[ndsipa_pomu]

Yes absolutely. I did not intend my suggestion to be interpreted as any kind of criticism.