Exception for (+ (pow x 20) (pow x (- 20)))

Math

\[{x}^{20} + {x}^{\left(-20\right)}\]

Reproduce

herbie shell --seed 2020153 
(FPCore (x)
  :name "(+ (pow x 20) (pow x (- 20)))"
  :precision binary64
  (+ (pow x 20.0) (pow x (neg 20.0))))