Expansion of g.f. (1 - sqrt(1 - 2*x + 2*x*sqrt(1 - 4*x)))/(2*x).

Terms

a(0) =0a(1) =1a(2) =1a(3) =3a(4) =7a(5) =21a(6) =62a(7) =197a(8) =637a(9) =2123a(10) =7196a(11) =24807a(12) =86608a(13) =305792a(14) =1089810a(15) =3915789a(16) =14169457a(17) =51592561a(18) =188888760a(19) =694946257a(20) =2568035734a(21) =9527251374a(22) =35472258506a(23) =132502639491a(24) =496423643176