The Norwegian mathematician Abel wrote in 1826 [1] “On the whole, divergent series are a devilry, and it is a shame to base any demonstration upon them”. At the other extreme Heaviside, a British physicist and engineer whose unorthodox methods raised many mathematical eyebrows, is quoted [2] as having said “The series is divergent; therefore we may be able to do something with it”. Heaviside may be accused of exaggeration but Abel, though his attitude was very reasonable in the absence of a proper theory of divergent series, was somewhat over-zealous in his total condemnation of the use of such series. Divergent series can be useful and in some cases are of far greater practical value than their convergent counterparts.