  In the presence of a sharp corner in the boundary of the entanglement region,
the entanglement entropy (EE) and Renyi entropies for 3d CFTs have a
logarithmic term whose coefficient, the corner function, is scheme-independent.
In the limit where the corner becomes smooth, the corner function vanishes
quadratically with coefficient $\sigma$ for the EE and $\sigma_n$ for the Renyi
entropies. For a free real scalar and a free Dirac fermion, we evaluate
analytically the integral expressions of Casini, Huerta, and Leitao to derive
exact results for $\sigma$ and $\sigma_n$ for all $n=2,3,\dots$. The results
for $\sigma$ agree with a recent universality conjecture of Bueno, Myers, and
Witczak-Krempa that $\sigma/C_T = \pi^2/24$ in all 3d CFTs, where $C_T$ is the
central charge. For the Renyi entropies, the ratios $\sigma_n/C_T$ do not
indicate similar universality. However, in the limit $n \to \infty$, the
asymptotic values satisfy a simple relationship and equal $1/(4\pi^2)$ times
the asymptotic values of the free energy of free scalars/fermions on the
$n$-covered 3-sphere.
