G.f. (1-x)/(7*x^2-6*x+1).

Terms

a(0) =1a(1) =5a(2) =23a(3) =103a(4) =457a(5) =2021a(6) =8927a(7) =39415a(8) =174001a(9) =768101a(10) =3390599a(11) =14966887a(12) =66067129a(13) =291634565a(14) =1287337487a(15) =5682582967a(16) =25084135393a(17) =110726731589a(18) =488771441783