Dodgson condensation

Summary

Dodgson condensation is a method to compute the determinant of a square matrix by repeatedly replacing it with a smaller matrix of connected $2 \times 2$ minors. Each step divides by interior entries of the matrix from two steps before. It rests on the Desnanot–Jacobi identity, a case of Sylvester's determinant identity. It was proposed by Charles Dodgson, better known as Lewis Carroll.