Table 1.

Forward and reverse linear feedback shift register (LFSR) with three different sizes (the rectangles stand for D flip-flops).

The Length of LFSR	Feedback Polynomials for Forward Counting	Feedback Polynomials for Reverse Counting
3 bits	$x^3+x^2+1$	$x^3+x^1+1$
4 bits	$x^4+x^3+1$	$x^4+x^1+1$
5 bits	$x^5+x^3+1$	$x^4+x^1+1$