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![{\displaystyle \sum _{n=1}^{\infty }\,{\frac {1}{n}}\;\;=\;\;1\,+\,{\frac {1}{2}}\,+\,{\frac {1}{3}}\,+\,{\frac {1}{4}}\,+\,{\frac {1}{5}}\,+\,\cdots .\!}](https://wikimedia.org/api/rest_v1/media/math/render/svg/4e15948216b708718574eb69a79d049a3701ba92)
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E-mail from Wikimedia foundation. 2.nov.2008
E-mail from Wikimedia foundation. 23.dec.2008
E-mail from Wikimedia foundation. 10.sept.2009
E-mail from Wikimedia foundation. 23.nov.2009
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Performed by Romuald Greiss on an 1850 Budynowicz piano
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E-mail from Wikimedia foundation. 17.oct.2012
E-mail from Wikimedia foundation. 21.May.2013
"Für Elise", opening
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![{\displaystyle 12*[[mydonation]]*\sum _{n=1}^{\infty }{\frac {1}{n^{2}}}=\lim _{n\to +\infty }\left({\frac {1}{1^{2}}}+{\frac {1}{2^{2}}}+\cdots +{\frac {1}{n^{2}}}\right).}](https://wikimedia.org/api/rest_v1/media/math/render/svg/aa45b60114f3d177ed2ef1de59e3c995db024688)