Exploring the series a bit in Excel led to a fortuitous observation that An^2An+.5 seems to asymptotically approach n from below before An gets very large. Using this observation one gets:
If An=2020, n is very close to 4078380.5, therefore min n=4078381
If An=2021, n is very close to 4082420.5, therefore max n=4082420
4078381<=n<=4082420 may be the solution?
Not sure why the series leads to this relation? Anyone?

Posted by Kenny M
on 20201028 11:17:06 