  This is an exposition of the theorem from the title, which says that the
number of self-avoiding walks with n steps in the hexagonal lattice has
asymptotics (2cos(pi/8))^{n+o(n)}. We lift the key identity to formal level and
simplify the part of the proof bounding the growth constant from below. In our
calculation the lower bound comes from an identity asserting that a linear
combination of 288 generating functions counting self-avoiding walks in a
certain domain by length, final edge direction and winding number modulo 48
equals the geometric series 2cos(pi/8)x + (2cos(pi/8))^2x^2 + ... .
