In 1997, the Texas banker Andrew Beal noticed that for any solution of Aˣ+Bʸ=Cᶻ he could find, A,B,and C had a common factor (e.g. 3⁶+18³=3⁸, 3 is a common factor). There's currently a $1 million prize for a proof or counterexample of the Beal conjecture.