p-INVERT of (1,1,0,0,0,0,...), where p(S) = 1 - 3 S + S^2.

Terms

a(0) =3a(1) =11a(2) =37a(3) =126a(4) =427a(5) =1448a(6) =4909a(7) =16643a(8) =56424a(9) =191292a(10) =648529a(11) =2198680a(12) =7454090a(13) =25271280a(14) =85676131a(15) =290464093a(16) =984747891a(17) =3338548317a(18) =11318536416a(19) =38372746007a(20) =130093466328a(21) =441050269849