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

Terms

a(0) =1a(1) =0a(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) =-25669818476