If f, of, 1, equals, 2f(1)=2, f, of, 2, equals, 0f(2)=0 and f, of, n, equals, 2, f, of, n, minus, 1, minus, f, of, n, minus, 2f(n)=2f(n−1)−f(n−2) then find the value of f, of, 4f(4).