why i am getting error, even when it runs on another device
Perhaps look at docs for DiscreteLimit
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int = Integrate[1/(x^3 - 1), x];
Map[Framed, int, Infinity]
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You may have been typing \[RightArrow] instead of \[Rule]. They are not the same thing.
Also, beware that (a[n])^1/n is read as ((a[n])^1)/n.