-31381059609domain: ZAppears in sequencesa(n) = 3*a(n-1) - 9*a(n-2), with a(0)=0, a(1)=1.at n=23A190963Expansion of (4+3*x)/(1+3*x).at n=21A256096Dirichlet inverse of A133494, 3^(n-1).at n=22A349453