A Texas banker is upping the ante to $1 million for whoever solves a tricky problem that has dogged mathematicians since the 1980s. The Providence-based American Mathematical Society said Tuesday $1 million will be awarded for publication of a solution to the so-called Beal Conjecture, a number theory problem. D. Andrew Beal of Dallas first offered the Beal Prize in 1997 for $5,000. Over the years, the amount has grown. Michael Breen of the American Mathematical Society said a solution is more difficult than the one for a related problem, Fermat’s Last Theorem, which did not have a published solution for more than 300 years.