A 9 Solution of (A 9) is given by g n = ( ϕ λ ) n g 0 = x n g 0, A 10 where x = ϕ/λ.
To proceed further, we substitute (A 3) into (A 2): ( s n + λ + ϕ ) ( f n − s b n ) = ϕ ( f n − 1 − s b n − 1 ) + λ ( f n + 1 − s b n + 1 ).