G.f.: ( 1 - x^2 - sqrt( 1 - 2*x^2 - 4*x^3 - 3*x^4 ) ) / ( 2*x^3 ).

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =3a(5) =5a(6) =9a(7) =16a(8) =29a(9) =54a(10) =101a(11) =191a(12) =365a(13) =702a(14) =1359a(15) =2647a(16) =5181a(17) =10187a(18) =20113a(19) =39856a(20) =79243a(21) =158036a(22) =316053a(23) =633689a(24) =1273559a(25) =2565136a(26) =5177043a(27) =10468199a(28) =21204379a(29) =43022215