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

Terms

a(0) =1a(1) =0a(2) =3a(3) =3a(4) =6a(5) =12a(6) =27a(7) =63a(8) =153a(9) =381a(10) =969a(11) =2505a(12) =6564a(13) =17394a(14) =46533a(15) =125505a(16) =340902a(17) =931716a(18) =2560401a(19) =7070337a(20) =19609146a(21) =54597852a(22) =152556057a(23) =427642677a(24) =1202289669a(25) =3389281245a(26) =9578183391a(27) =27130207503a(28) =77009455428a(29) =219023318406