Shifts 2 places left under binomial transform.

Terms

a(0) =1a(1) =0a(2) =1a(3) =1a(4) =2a(5) =5a(6) =13a(7) =36a(8) =109a(9) =359a(10) =1266a(11) =4731a(12) =18657a(13) =77464a(14) =337681a(15) =1540381a(16) =7330418a(17) =36301105a(18) =186688845a(19) =995293580a(20) =5491595645a(21) =31310124067a(22) =184199228226