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I found the logo from The Eighth Congress of Romanian Mathematicians. I think this is the von Mangoldt summatory function and with a simple computation, using this definition, I obtained $83$. Am I wrong or how can the following be true?$$ \sum_{i=1929}^{2015}\Lambda(i)=8 $$

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    $\begingroup$ Apparently their $\Lambda$ is not the von Mangoldt function. $\endgroup$ Commented Jun 30, 2015 at 16:03
  • $\begingroup$ The Seventh congress used $\chi$ as the function and had an upper limit of 2011. The Sixth was in 2007, I don't recall whether this "joke" was used there. $\endgroup$ Commented Jun 30, 2015 at 23:34

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Perhaps

$$\Lambda(i)= \begin{cases} 1\quad\text{if a Congress was held in year }i\\ 0\quad\text{otherwise} \end{cases} $$

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Note the indices of summation look a lot like years; $\Lambda : \mathbb{N} \to \{0, 1\}$ is the function indicating whether that year had a Congress of Romanian Mathematicians.

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    $\begingroup$ Great minds think alike.... ;-) $\endgroup$ Commented Jun 30, 2015 at 16:13

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