Expansion of 3*(1+x)/(1-2*x-5*x^2).

Terms

a(0) =3a(1) =9a(2) =33a(3) =111a(4) =387a(5) =1329a(6) =4593a(7) =15831a(8) =54627a(9) =188409a(10) =649953a(11) =2241951a(12) =7733667a(13) =26677089a(14) =92022513a(15) =317430471a(16) =1094973507a(17) =3777099369a(18) =13029066273a(19) =44943629391a(20) =155032590147a(21) =534783327249