(1)T4=a1*a2*a3*a4=1*3*5*7=105(2)n=1,a1=T1=1n≥2 an=Tn/T(n-1)=n²/(n-1)²
1),T4=a1*a2*a3*a4=(2*1-1)(2*2-1)(2*3-1)(2*4-1)=1*3*5*7=1052),an=Tn/T(n-1)=n^2/(n-1)^2=(n/(n-1))^2.......n>=2; an=Tn=T1=1^2=1...............n=1;