summation ((1/n)*x**n,(n,1,oo ))
solve(Piecewise((-log(1 - x), (x >= -1) & (x < 1)), (Sum(x**n/n, (n, 1, oo)), True)), n)
diff(Piecewise((-log(1 - x), (x >= -1) & (x < 1)), (Sum(x**n/n, (n, 1, oo)), True)), n)
series(Piecewise((-log(1 - x), (x >= -1) & (x < 1)), (Sum(x**n/n, (n, 1, oo)), True)), n, 0, 10)
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