**Matrix Expansions for Computing the Discrete
Hartley Transform for blocklength N=0 (mod 4)**

A new fast algorithm for computing the discrete Hartley transform (DHT) is presented,

which is based on the expansion of the transform matrix.

The algorithm presents a better performance, in terms of multiplicative complexity,

than previously known fast Hartley transform algorithms and same

performance, in terms of additive complexity, than Split-Radix algorithm.

A detailed description of the computation of DHTs with blocklengths 8 and 16 is shown.

The algorithm is very attractive for blocklengths N > 128.