Given a general, convergent infinite sum, say, one like this:(adsbygoogle = window.adsbygoogle || []).push({});

[tex]\sum_{n=0}^\infty a_n x^n[/tex]

Is there a formula for the square of such a sum? I looked at the Cauchy product, but I'd rather not get a double sum as an answer...

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# Square of an infinite sum

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