contraharmonic mean

Etymology
The contraharmonic mean of two variables is at the same distance from their arithmetic mean as their harmonic mean but on the opposite side.

Noun

 * 1)  A type of average calculated as the arithmetic mean of the squares of the values divided by the arithmetic mean of the values, ie. $$C = { {( x_1^2 + x_2^2 + ... + x_n^2) \over n } \over { ( x_1 + x_2 + ... + x_n ) \over n } }\ or \ C(x_1, x_2, ..., x_n) ={ { x_1^2+x_2^2+...+x_n^2} \over {x_1+x_2+...+x_n }} $$

Translations

 * Finnish: kontraharmoninen keskiarvo
 * Serbo-Croatian: kontraharmonijska sredina