This suggests that there may exist a sequence of constants {an}∞
n=0 such that (Pn +
In)−1 = Pn ◦ Δn, where the matrix Δn is a lower triangular matrix with generic element
Δn(i, j) = ai−j when i ≥ j. Aggarwala and Lamoureux [2] have showed that these constants
are values of the Dirichlet eta function evaluated at negative integers, or more generally,
certain polylogarithm functions evaluated at the number −1