A series is the indicated sum of the terms of a sequence.
Finite sequence : 3, 7, 11, 15, 19
Related finite series : 3 + 7 + 11 + 15 + 19
Infinite sequence :
Related infinite series :
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.”