Fast multidimensional discrete Hartley transform using Fermat number transform

It is shown that by using an index mapping scheme, the multidimensional discrete Hartley transform can be changed into convolutions that can be calculated very efficiently via the Fermat number transform. Compared with existing algorithms, the number of multiplications is reduced by a factor of 8 to 20, at the expense of a slight increase in the number of shift and add operations, that are assumed to be simpler than multiplications