Toeplitz antisymmetric tridiagonal matrix (source code)

= Toeplitz antisymmetric tridiagonal matrix
{c}

An $M\times M$ Toeplitz antisymmetric tridiagonal matrix with diagonal $a$, superdiagonal $b$, and subdiagonal $-b$ has eigenvalues
$$
\lambda_j=a+2ib\cos\frac{j\pi}{M+1},
\qquad 1\leq j\leq M.
$$
All such matrices share an orthonormal eigenbasis after the same diagonal unitary change from the discrete sine basis.