von Mangoldt function
properNoun
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(math) A certain arithmetic function that is neither multiplicative nor additive. It is denoted by Λ(n) and defined as :\Lambda(n) = \begin{cases} \log p & \mbox{if }n=p^k \mbox{ for some prime } p \mbox{ and integer } k \ge 1, \\ 0 & \mbox{otherwise.} \end{cases}