What is the closed-form solution to an=an−1+2n−1a_n = a_{n-1} + 2n - 1an=an−1+2n−1 with a0=0a_0 = 0a0=0?
an=na_n = nan=n
an=n2a_n = n^2an=n2
an=n(n+1)a_n = n(n+1)an=n(n+1)
an=2na_n = 2^nan=2n