G.f.: 1/(1-2x-19x^2)^(1/2).

Terms

a(0) =1a(1) =1a(2) =11a(3) =31a(4) =211a(5) =851a(6) =4901a(7) =22961a(8) =124531a(9) =623011a(10) =3313201a(11) =17086301a(12) =90453661a(13) =473616781a(14) =2509264811a(15) =13250049551a(16) =70368250451a(17) =373539254611