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billion

, the sequence {cn} is a arithmetic progression with 1 as the first term and a tolerance of 2, and the general term formula of the sequence {cn} can be obtained;

(2) Dislocation subtraction summation.

( 1)∵anbn+ 1？ an+ 1bn+2bn+ 1bn=0，cn=anbn，

∴cn？ cn+ 1+2=0，

∴cn+ 1？ cn=2，

∫ Two series whose first term is 1 {an}, {bn}

∴ Sequence {cn} is a arithmetic progression, the first term is 1, and the tolerance is 2.

∴cn=2n？ 1;

(2)∵bn=3n？ 1，cn=anbn，

∴an=(2n？ 1)? 3 1? n，

∴Sn= 1×30+3×3？ 1+…+(2n？ 1)×3 1? n，

∴3Sn= 1×3+3×30+…+(2n？ 1)×32? n，

∴? 2Sn=？ 1×3? 2? (30+3? 1+…+32? n)？ (2n？ 1)? 3 1? n，

∴Sn=(n？ 1)3 1? n+3。