112846domain: NAppears in sequencesCoefficient of x^floor(n/2) in the expansion of (1+x+x^3)^n.at n=17A192440Triangle read by rows: T(n,g) = number of general immersions of a circle with n crossings in a surface of arbitrary genus g, in the case that the circle is oriented and the surface is oriented.at n=22A260285