Both $a$ and $b$ are divisible by 6

$\frac{a}{6}$ and $\frac{b}{6}$ are coprime (i.e., $\gcd(a/6, b/6) = 1$)

$\text{lcm}(a,b) = \frac{ab}{6}$

Both $a$ and $b$ have only 2 and 3 as prime factors