Number of self-avoiding walks on a 2-D lattice of length n which start at the origin, take first step in the {+1,0} direction and whose vertices are always nonnegative in x and y.

A046170

Number of self-avoiding walks on a 2-D lattice of length n which start at the origin, take first step in the {+1,0} direction and whose vertices are always nonnegative in x and y.