a(n) = a(n-1) + 4*a(n-3) + 2*a(n-4) + 2*a(n-5); a(0) = a(1) = a(2) = 1, a(3) = 5, a(4) = 11.

Terms

a(0) =1a(1) =1a(2) =1a(3) =5a(4) =11a(5) =19a(6) =43a(7) =99a(8) =207a(9) =439a(10) =959a(11) =2071a(12) =4439a(13) =9567a(14) =20647a(15) =44463a(16) =95751a(17) =206351a(18) =444631a(19) =957855a(20) =2063687a(21) =4446415a(22) =9579799a(23) =20639519a(24) =44468263a(25) =95807663a(26) =206418167a(27) =444729855a(28) =958176071