+0

0
124
1
+79

The closed form sum of

$$12 \left[ 1^2 \cdot 2 + 2^2 \cdot 3 + \ldots + n^2 (n+1) \right]$$

for $$n \geq 1$$ is $$n(n+1)(n+2)(an+b).$$ Find $$an + b.$$

Apr 10, 2021