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

Terms

a(0) =1a(1) =3a(2) =17a(3) =99a(4) =609a(5) =3843a(6) =24689a(7) =160611a(8) =1054657a(9) =6975747a(10) =46406097a(11) =310171491a(12) =2081258529a(13) =14011445763a(14) =94594402353a(15) =640188979299