The notation "Σb_n" represents the summation of a sequence of terms denoted by b_n. In mathematics, the symbol "Σ" (sigma) indicates that we are adding together a series of values. The subscript "n" typically indicates the index of the terms being summed, which can range from a starting value to an ending value. For example, if b_n represents the sequence of numbers 1, 2, 3, ..., then Σb_n from n=1 to n=3 would equal 1 + 2 + 3, resulting in a total of 6. Summations like Σb_n are fundamental in various fields, including calculus and statistics, for analyzing data and understanding patterns.