(1)设bn=log2(an+1),则{bn}为等差数列,又a1=1,a3=7,所以b1=log2(1+1)=1,b2=log(7+1)=3,所以公差d=1.所以bn=b1+(n-1)d=1+(n-1)=n,因此,log2(an+1)=n,所以an+1=2^n,即an=2^n-1.(2)数列{an}是由等比数列{2^n}与常数列组...