Expansion of g.f. (1-z)^2*(1-sqrt(1-4*z))/(2*z*(1 - 3*z + 2*z^2 - z^3)).

Terms

a(0) =1a(1) =2a(2) =5a(3) =14a(4) =40a(5) =116a(6) =344a(7) =1047a(8) =3273a(9) =10500a(10) =34503a(11) =115838a(12) =396244a(13) =1377221a(14) =4851665a(15) =17285662a(16) =62173297a(17) =225424527a(18) =822919439a(19) =3021713140a(20) =11151957809a(21) =41340655956a(22) =153853915410a(23) =574593145517