1016978784domain: NAppears in sequencesa(2*n) = 3*a(2*n-1), a(2*n+1) = 3*a(2*n) - 1, with a(1) = 1.at n=19A153774Expansion of (1 + 8*x - 6*x^2 + 12*x^3 - 18*x^4)/(1 - x - 9*x^4 + 9*x^5).at n=38A309791