If You have two sequences and , then their 'correlation product' is by definition the sequence that has general term...

(1)

If You denote with the Z-transform of , the Z-transform of and the Z-transform of , then You have the well known relation...

(2)

If You have , that means that is and is...

(3)

... so that (2) becomes...

(4)

Marry Christmas from Serbia