Affine inequivalence of cubic Maiorana–McFarland type bent functions

We consider cubic Maiorana–McFarland type bent functions having no affine derivatives. By using an invariant proposed by Dillon in 1975 we identify subclasses of inequivalent bent functions within this class. These can also be identified by [4, Theorem B]. However, our technique involves only elementary derivations. We also include some computational results.