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

Terms

a(0) =1a(1) =1a(2) =-1a(3) =2a(4) =-5a(5) =13a(6) =-35a(7) =99a(8) =-289a(9) =857a(10) =-2578a(11) =7864a(12) =-24252a(13) =75430a(14) =-236348a(15) =745431a(16) =-2364399a(17) =7536482a(18) =-24127482a(19) =77544613a(20) =-250098478a(21) =809169322a(22) =-2625483810a(23) =8541037140a(24) =-27851360659a(25) =91018956200a(26) =-298052119611a(27) =977825373366