a(0) = 1, a(1) = 2; for n>1, a(n) = a(n-1) + a(n-2) + 4.

Terms

a(0) =1a(1) =2a(2) =7a(3) =13a(4) =24a(5) =41a(6) =69a(7) =114a(8) =187a(9) =305a(10) =496a(11) =805a(12) =1305a(13) =2114a(14) =3423a(15) =5541a(16) =8968a(17) =14513a(18) =23485a(19) =38002a(20) =61491a(21) =99497a(22) =160992a(23) =260493a(24) =421489a(25) =681986a(26) =1103479a(27) =1785469a(28) =2888952a(29) =4674425