G.f. A(x) satisfies A(x) = ( 1 + 4*x*A(x)/(1 - x) )^(1/2).

Terms

a(0) =1a(1) =2a(2) =4a(3) =6a(4) =6a(5) =2a(6) =-4a(7) =-2a(8) =20a(9) =50a(10) =24a(11) =-130a(12) =-302a(13) =-14a(14) =1176a(15) =2166a(16) =-874a(17) =-10494a(18) =-15464a(19) =15886a(20) =95006a(21) =107586a(22) =-210624a(23) =-860234a(24) =-686084a(25) =2499602a(26) =7733116a(27) =3460038a(28) =-27992190a(29) =-68487790