205928262674domain: NAppears in sequencesa(n) = 6*a(n-1) - a(n-2), n >= 2, a(0)=1, a(1)=4.at n=15A038723Solutions (value of r) of the Diophantine equation 2*x^2 + 3*x + 2 = r^2.at n=14A055979Expansion of (1 + 6*x + 17*x^2 - x^3 - 3*x^4)/(1 - 6*x^2 + x^4).at n=28A227792