Contraharmonic (Lehmer) mean of a list
ContraharmonicMean[list]
ContraharmonicMean[list, p]
ContraharmonicMean[{a, b, c, d}]
→ (a^2 + b^2 + c^2 + d^2)/(a + b + c + d)ContraharmonicMean[{{1, 2}, {5, 4}, {6, 7}}]
→ {31/6, 69/13}ContraharmonicMean[{1, 2, 3, 4}]
→ 3