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

Terms

a(0) =1a(1) =2a(2) =4a(3) =4a(4) =0a(5) =-8a(6) =-8a(7) =16a(8) =48a(9) =0a(10) =-192a(11) =-256a(12) =480a(13) =1792a(14) =320a(15) =-7808a(16) =-12544a(17) =19200a(18) =87808a(19) =33280a(20) =-382464a(21) =-720896a(22) =854016a(23) =4870144a(24) =2844160a(25) =-20553728a(26) =-44909568a(27) =38967296a(28) =289456128a(29) =228986880