1, superscript: n represents the upper bound, which refers to the elements in a poset that are greater than or equal to all the elements in its subset.
2. Subscript: I stands for the lower limit. If a set of real numbers M has a real number S, so that any number in M is greater than S, then S is called a lower bound of M. ..
Extended data:
Capital σ is used for mathematical summation symbols, such as ∑Pi, where i= 1, 2, ..., t, which is the sum of P 1+P2+ and ...+angle. Lowercase σ is used for statistical standard deviation. Both the с of Cyrillic alphabet and the S of Latin alphabet are derived from Sigma.
It also means summation, which means ∑ j =1+2+3+…+n.