Define the sequence an=(n−1)an−1a_n = (n-1) a_{n-1}an=(n−1)an−1 for n≥2n \geq 2n≥2 with a1=1a_1 = 1a1=1. What is the closed form for ana_nan?
n!n!n!
(n−1)!(n-1)!(n−1)!
2n−12^{n-1}2n−1
(n2)\binom{n}{2}(2n)