ヘルダー平均
M − 1 ( x 1 , ... , x n ) = n 1 x 1 + ⋯ + 1 x n {\displaystyle M_{-1}(x_{1},\dots ,x_{n})={\frac {n}{{\frac {1}{x_{1}}}+\dots +{\frac {1}{x_{n}}}}}}