Find the product of the first nnn terms of a geometric sequence.
(a1an)n/2(a_1 a_n)^{n/2}(a1an)n/2
a1nrn(n−1)/2a_1^n r^{n(n-1)/2}a1nrn(n−1)/2
a1nrn2a_1^n r^{n^2}a1nrn2
Both a and b