Find closed form of series SUM (nx)^(2n)

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The forum discussion focuses on finding a closed form for the series SUM (nx)^(2n) for |x| < 1. The key approach involves using the relationship sum n*x^n = x*sum n*x^(n-1) and applying differentiation techniques. Participants emphasize the importance of manipulating the series through integration and differentiation to derive the closed form function. The final closed form is established as f(x) = x/(1-x^2)^2.

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If abs x < 1 find a closed form function (i.e. f(x) = x +1) for the following series:

\sum((nx)^(2n))

(reads: the series from n=1 to infinity of nx^(2n))
 
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Try to first find an equation for sum n*x^n = x*sum n*x^(n-1) using integration/differentiation.
 

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