（1）当n≥2时，an=Sn-Sn-1=n（2n-1）an-（n-1）（2n-3）an-1，得anan−1＝2n−32n+1∴a2a1a3a2a4a3a5a4…an−1an−2anan−1＝15×37×59×711…2n−52n−1×2n−32n+1又a1＝13得an＝1(2n−1)(2n+1)（2）因为Sn=n（2...