Page "Discrete Hartley transform" Paragraph 2

Formally, the discrete Hartley transform is a linear, invertible function H: R < sup > n </ sup > < tt >-></ tt > R < sup > n </ sup > ( where R denotes the set of real numbers ).

The N real numbers x < sub > 0 </ sub >, ...., x < sub > N-1 </ sub > are transformed into the N real numbers H < sub > 0 </ sub >, ..., H < sub > N-1 </ sub > according to the formula