134217714domain: NAppears in sequencesa(n) = 3*a(n-1) - a(n-2) - 3*a(n-3) + 2*a(n-4).at n=27A084174Expansion of o.g.f. x*(1 - x + x^2)/(1 -3*x +x^2 +3*x^3 -2*x^4).at n=27A173009