 James Propp defines a regularized Euler measure for polyhedral sets that, in this example, replaces with , sums the series for |"t"| < 1, and analytically continues to "t" = 1, essentially finding the Abel sum of , which is 1/2.Generally, he finds χ(2"A") = 2χ("A") for any polyhedral set "A", and the base of the exponent generalizes to other sets as well.Infinite-dimensional real projective space RP∞ is another structure with one cell of every dimension and therefore an Euler characteristic of .