Expansion of g(x) - x*g(x^2), where g(x) is the g.f. of A001405.

Terms

a(0) =1a(1) =0a(2) =2a(3) =2a(4) =6a(5) =8a(6) =20a(7) =32a(8) =70a(9) =120a(10) =252a(11) =452a(12) =924a(13) =1696a(14) =3432a(15) =6400a(16) =12870a(17) =24240a(18) =48620a(19) =92252a(20) =184756a(21) =352464a(22) =705432a(23) =1351616a(24) =2704156a(25) =5199376a(26) =10400600a(27) =20056584a(28) =40116600a(29) =77555328