(Ⅰ)∵a1=4,an+1=3an-4n+2(n∈N*).
∴an+1-2(n+1)=3(an-2n),(n∈N*).
即bn+1=3bn,
则数列{bn}是等比数列公比q=3,首项a1-2=4-2=2;
(Ⅱ)∵数列{bn}是等比数列公比q=3,首项a1-2=4-2=2;
∴bn=2×3n-1,即an-2n=2×3n-1,
an=2×3n-1+2n,
则数列{an}的前项和Sn=2(1+3+…+3n-1)+2(1+2+…n)=2×
1?3n
1?3+n(n+1)=3n-1+n(n+1).
(Ⅰ)∵a1=4,an+1=3an-4n+2(n∈N*).
∴an+1-2(n+1)=3(an-2n),(n∈N*).
即bn+1=3bn,
则数列{bn}是等比数列公比q=3,首项a1-2=4-2=2;
(Ⅱ)∵数列{bn}是等比数列公比q=3,首项a1-2=4-2=2;
∴bn=2×3n-1,即an-2n=2×3n-1,
an=2×3n-1+2n,
则数列{an}的前项和Sn=2(1+3+…+3n-1)+2(1+2+…n)=2×
1?3n
1?3+n(n+1)=3n-1+n(n+1).