Many problems in mathematics require one to estimate a sum when it is not feasible to evaluate the sum exactly. This article contains links to articles that discuss techniques relevant to this general task.
Partial summation When is this useful? ( If you have a sum of the form , partial summation allows you to replace the sequences and by the difference sequence and the partial-sums sequence . Partial summation is useful if the sum is easier to handle than the sum . (It is the discrete analogue of integration by parts.))