http://mathworld.i2p/UnimodularMatrix.html
The th power of a unimodular matrix (3) is given by (4) where (5) and the are Chebyshev polynomials of the second kind , (6) (Born and Wolf 1980, p. 67). See also Chebyshev Polynomial of the Second Kind , Determinant , Identity Matrix , Unit Matrix References Born, M. and Wolf, E.