1.NounAny expression that represents the addition a countably infinite number of ordered summands, often explicitly indexed by the positive or nonnegative integers.
"In 1734, Leonhard Euler solved the Basel problem by summing the infinite series
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{\displaystyle \textstyle {\frac {1}{1^{2}}}+{\frac {1}{2^{2}}}+{\frac {1}{3^{2}}}+\cdots =\sum _{n=1}^{\infty }{\frac {1}{n^{2}}}={\frac {\pi ^{2}}{6}}}
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