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

Terms

a(0) =0a(1) =1a(2) =1a(3) =1a(4) =2a(5) =4a(6) =9a(7) =21a(8) =51a(9) =127a(10) =323a(11) =835a(12) =2188a(13) =5798a(14) =15511a(15) =41835a(16) =113634a(17) =310572a(18) =853467a(19) =2356779a(20) =6536382a(21) =18199284a(22) =50852019a(23) =142547559a(24) =400763223a(25) =1129760415a(26) =3192727797a(27) =9043402501a(28) =25669818476a(29) =73007772802