Summation of Grandi's Series

Summation Of Grandi's Series

The formal manipulations that lead to 1 − 1 + 1 − 1 + · · · being assigned a value of 1⁄2 include:

  • Adding or subtracting two series term-by-term,
  • Multiplying through by a scalar term-by-term,
  • "Shifting" the series with no change in the sum, and
  • Increasing the sum by adding a new term to the series' head.

These are all legal manipulations for sums of convergent series, but 1 − 1 + 1 − 1 + · · · is not a convergent series.

Nonetheless, there are many summation methods that respect these manipulations and that do assign a "sum" to Grandi's series. Two of the simplest methods are Cesàro summation and Abel summation.

Read more about Summation Of Grandi's Series:  Cesàro Sum, Abel Sum, Separation of Scales, Borel Sum, Spectral Asymmetry, Proof Through 1 / X Series, Methods That Fail

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