The antiharmonic, a.k.a. contraharmonic mean of some set of positive numbers is defined as the sum of their squares divided by their sum. There exist positive integers whose sum of all their positive divisors divides the sum of the squares of those divisors. For example, 4 is such an integer:
Such integers are called antiharmonic numbers (or contraharmonic numbers), since the contraharmonic mean of their positive divisors is an integer.
The antiharmonic numbers form the HTTP://oeis.org/OEIS integer sequence http://oeis.org/search?q=A020487&language=english&go=SearchA020487:
Note. It would in a manner be legitimated to define a positive integer to be an antiharmonic number (or an antiharmonic integer) if it is the antiharmonic mean of two distinct positive integers; see integer contraharmonic mean and contraharmonic Diophantine equation (http://planetmath.org/ContraharmonicDiophantineEquation).
|Date of creation||2013-11-28 10:15:29|
|Last modified on||2013-11-28 10:15:29|
|Last modified by||pahio (2872)|