10485756domain: NAppears in sequencesa(n) = T(4,n), array T given by A048483.at n=21A048487a(n) is one fourth of the total number of free ends of 4 line segments expansion at n iterations (see Comments lines for definition).at n=42A238549Expansion of (x - x^2 + 2*x^3 + 2*x^4)/(1 - 3*x + 2*x^2).at n=23A270810