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Series

A series is the indicated sum of the terms of a sequence.

A series can be written in an abbreviated form by using the Greek letter ∑ (sigma), called the summation sign.  For instance, to abbreviate the writing of the series 2 + 4 + 6 + 8 + ··· + 50 first notice that the general term of the series is 2n.  The series begins with the term for n = 1 and ends with the term for n = 25.  Using sigma notation, you can write this series as , which is read “the sum of 2n for values of n from 1 to 25.”