由条件,f(2) = 2f(1) + 1f(3) = f(1) + f(2) + 2= 3f(1) + 3所以f(1) =1令m = 1,得f(n+1) = f(n) + f(1) + n= f(n) + n+1这是一个数列问题,f(n) = f(n-1) + n= f(n-2) + n + (n-1)= ...= f(1) + n + (n-1) + ...+ 2=...