PutnamSuperchallengeIntegrals I: Feynman's Trick ShareIntegrals I: Feynman's Trick · Superchallenge problemEvaluate ∑n=1∞n3n\displaystyle\sum_{n=1}^{\infty} \dfrac{n}{3^n}n=1∑∞3nn. Express your answer as a common fraction.Check Show answer Walk through it step by step Practice more like this Review this concept