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