Number of length n+2 0..1 arrays with at most two downsteps in every n consecutive neighbor pairs.

Terms

a(0) =8a(1) =16a(2) =32a(3) =64a(4) =124a(5) =229a(6) =402a(7) =673a(8) =1080a(9) =1670a(10) =2500a(11) =3638a(12) =5164a(13) =7171a(14) =9766a(15) =13071a(16) =17224a(17) =22380a(18) =28712a(19) =36412a(20) =45692a(21) =56785a(22) =69946a(23) =85453a(24) =103608a(25) =124738a(26) =149196a(27) =177362a(28) =209644a(29) =246479