472448domain: NAppears in sequencesa(n) = 2*a(n-1) + 2*a(n-2) for n > 1; a(0)=2, a(1)=2.at n=13A080040a(n) = floor((1+sqrt(3))^n).at n=13A080041Expansion of 2*(1+2*x) / (1-8*x+4*x^2).at n=6A270444