Dark Energy from Catalan's Constant

This short note shows that the dark–energy density parameter can be writtenin a parameter–free form: ΩΛ = 1 − G/π = 0.7084, where G = β(2) is Catalan’s constant (the value of the Dirichlet betafunction at s = 2). This prediction agrees with Planck 2018 observations within a few standard deviations.No free parameters or fitting are required.A full theoretical derivation will be presented in a separate paper.