Moderate# Fermat Number: Finding GCD and LCM

NUMTH-RVPLOZ

Fermat number is a positive integer of the form:

$$ F_n = 2^{2^n}+1 $$

...for a nonnegative integer $n$.

What is the least common multiple of $F_m$ and $F_n$? Select **ONE** answer which is always true.