n≥2时,a[n]=S[n]-S[n-1]=2a[n+1]+1-2a[n]-1∴3a[n]=2a[n+1]即：a[n+1]/a[n]=3/2∴当n≥2时数列{a[n]}是公比为3/2的等比数列∵a[1]=3 a[1]=S[1]=2a[2]+1 ∴a[2]=1∴n=1时 a1=3n≥2时 a[n]=1*(3/2)^(n-2)=(3/2)^(n-2)...