S3=3a1+3d≤9a1+d≤3a2≤3a4>3,a4>a2,a4=a2+2d>a2 d>0,公差d>0,数列为递增数列.a1>1,又a1为整数,a1至少为2,又a2≤3,a1至多为2,因此a1=2 a2=3d=a2-a1=3-2=1an=a1+(n-1)d=2+n-1=n+1bn=2n×an=2n(n+1)=2n²+2nTn=b1...