Since the function is defined for all one can still take the limit as "x" approaches 1, and this is the definition of the Abel sum::formula_10===Euler and Borel===Euler applied another technique to the series: the Euler transform, one of his own inventions.
Leta 1887 je Cesàro prišel blizu definicije vsote (C, "n"), vendar je podal le nekaj primerov.