11957421domain: NAppears in sequencesa(n) = 3*(a(n-2) + 1), with a(0) = 1, a(1) = 3.at n=28A087503Expansion of x*(1+x+2*x^3) / ((x-1)*(1+x)*(3*x^2-1)).at n=30A120463a(n) = (5*3^n-3)/2.at n=14A134931a(n) = 2*a(n-1) + 3*a(n-2), with a(0) = 1, a(1) = 9.at n=14A137340Expansion of (1+2*x+2*x^2-x^3)/((1-x)*(1+x)*(1-3x^2)).at n=28A220946