A very specific request!
One of the most popular algorithms for solving the symmetric eigenvalue problem is the QR algorithm, which was first proposed by John G.F. Francis and Vera N. Kublanovskaya in the early 1960s. The QR algorithm is an iterative method that uses the QR decomposition of a matrix to compute the eigenvalues and eigenvectors.
The problem can be reformulated as finding the eigenvalues and eigenvectors of the matrix A.