Number of length n+4 0..1 arrays with at most one downstep in every 4 consecutive neighbor pairs.

Terms

a(0) =26a(1) =45a(2) =80a(3) =144a(4) =256a(5) =451a(6) =796a(7) =1413a(8) =2510a(9) =4448a(10) =7872a(11) =13943a(12) =24718a(13) =43817a(14) =77636a(15) =137540a(16) =243712a(17) =431899a(18) =765360a(19) =1356169a(20) =2403034a(21) =4258172a(22) =7545592a(23) =13370799a(24) =23692770a(25) =41983189a(26) =74394040a(27) =131826104a(28) =233594880a(29) =413927683