is an option for Sum and Product that specifies what type of regularization to use.


  • Regularization affects only results for divergent sums and products.
  • The following settings can be used to specify regularization procedures for sums of the form :
  • "Abel"
  • For alternating sums , the setting "Euler" gives .
  • The following setting can be used to specify a regularization procedure for products :
  • "Dirichlet"
  • Regularization->None specifies that no regularization should be used.
  • For multiple sums and products, the same regularization is by default used for each variable.
  • Regularization->{reg1,reg2,} specifies regularization regi for the i^(th) variable.


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Basic Examples  (3)

The following sum does not converge:

Using Abel regularization will produce a finite value:

In this case the Abel-regularized sum does not exist:

However, the stronger Borel regularization produces a finite value:

A regularized value of a divergent product:

Scope  (5)

Apply Abel regularization to sum a divergent polynomial-exponential series:

Use Borel regularization to sum a divergent hypergeometric series:

Apply Cesaro regularization to sum a divergent trigonometric series:

Sum a divergent logarithmic series using Dirichlet regularization:

Apply Euler regularization to sum a divergent geometric series:

Applications  (1)

The regularized sum of all the natural numbers is :

Introduced in 2008