a(n) = aq^(n-1),a>0,q>0.
t(n) = a(1)a(2)...a(n-1)a(n) = a*aq*...*aq^(n-2)*aq^(n-1) = a^nq^[1+2+...+(n-1)]
= a^nq^[n(n-1)/2].
1 = t(9) = a^9q^[36] = [aq^4]^9,aq^4 = 1.
a(4)a(6) = aq^3*aq^5 = a^2q^8 = [aq^4]^2 = 1^2 = 1.