According to Wolfram Alpha, ∞∑n=11n(2n+1)(2n−1)=ln(4)−1 However, I am not sure how to evaluate this series.
Attempt 1n(2n+1)(2n−1)=An+B2n+1+C2n−1 1=A(2n+1)(2n−1)+Bn(2n−1)+Cn(2n+1)
Then, I got ∞∑n=11n(2n+1)(2n−1)=∞∑n=1−1n+12n+1+12n−1 I tried to view this as a telescoping series, but it did not turn out good. Can I have a hint?
Answer
∑n≥1(12n−1−12n)−∑n≥1(12n−12n+1)=ln2−(1−ln2)
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