∑ means continuous addition in mathematics.
Specific to this problem means
As for the denominator, when I take an integer from 1 to 1 1, it is brought into the formula on the right side of ∑ in turn, and the values of the formula are added together in turn as the denominator.
So do molecules.
So the whole formula = (1+2+3+4+5+11)/(1-2+3-4+5-6+7-+16544.
Please adopt