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