a x 2a2 x 3a3
You can see it when I write $$a^2 = a*a$$ and $$a^3 = a*a*a$$
$$a*2a^2*3a^3 = a * 2 * a * a * 3 * a * a * a = 2*3 * a * a * a * a * a * a = 6a^6$$