Number of inequivalent self-avoiding walks of length n on a 2-D lattice which start at origin, take first step in {+1,0} direction and if any steps are vertical, a step up is taken before a step down.

A046171

Number of inequivalent self-avoiding walks of length n on a 2-D lattice which start at origin, take first step in {+1,0} direction and if any steps are vertical, a step up is taken before a step down.