On Dirichlet eigenvalues of regular polygons

We prove that the first Dirichlet eigenvalue of a regular N-gon of area π has an asymptotic expansion of the form λ1(1+∑n≥3Cn(λ1)Nn) as N→∞, where λ1 is the first Dirichlet eigenvalue of the unit disk and Cn are polynomials whose coefficients belong to the space of multiple zeta values of weight n and conjecture that their coefficients lie in the space of single-valued multiple zeta values. We also explicitly compute these polynomials for all n≤14.