f(x)=(x+1/2)^2+1/4,x∈[n,n+1],n∈N+.
值域显然是[f(n),f(n+1)]=[n^2+n+1/2,n^2+3n+5/2]
其中的包含的整数有：n^2+n+1,n^2+n+2,...,n^2+3n+2
共有n^2+3n+2-(n^2+n+1)+1=2(n+1)个.