解答:(1)解:设公差为d≠0,
∵a3=6,且a1,a2,a4成等比数列,
∴a1+2d=6,且(a1+d)2=a1?(a1+3d),
解得a1=2,d=2.
∴数列{an}的通项公式为an=2+(n-1)×2=2n;
∵bn+1=2bn+1,
∴bn+1+1=2(bn+1),
∵b1=3,
∴数列{bn+1}是以4为首项,2为公比的等比数列,
∴bn+1=2n+1,
∴bn=2n+1-1;
(2)证明:cn=
=1
an?log2(bn+1)
=1 2n(n+1)
(1 2
-1 n
),1 n+1
∴Sn=
(1-1 2
+1 2
-1 2
+…+1 3
-1 n
)=1 n+1
(1-1 2
)<1 n+1
,1 2
∴Sn<
.1 2