Compute $$1\cdot 2^2+2\cdot 3^2+3\cdot4^2+\cdots+19\cdot 20^2.$$
Question:
Compute $$1\cdot 2^2+2\cdot 3^2+3\cdot4^2+\cdots+19\cdot 20^2.$$
Answer:
Let's think step by step.

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Compute $$1\cdot 2^2+2\cdot 3^2+3\cdot4^2+\cdots+19\cdot 20^2.$$
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