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

Terms

a(0) =1a(1) =2a(2) =1a(3) =2a(4) =-2a(5) =-4a(6) =-11a(7) =-22a(8) =-14a(9) =-28a(10) =58a(11) =116a(12) =316a(13) =632a(14) =397a(15) =794a(16) =-2198a(17) =-4396a(18) =-11954a(19) =-23908a(20) =-14684a(21) =-29368a(22) =95170a(23) =190340a(24) =517492a(25) =1034984a(26) =623764a(27) =1247528a(28) =-4462472a(29) =-8924944