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

Terms

a(0) =1a(1) =4a(2) =5a(3) =9a(4) =14a(5) =23a(6) =37a(7) =60a(8) =97a(9) =157a(10) =254a(11) =411a(12) =665a(13) =1076a(14) =1741a(15) =2817a(16) =4558a(17) =7375a(18) =11933a(19) =19308a(20) =31241a(21) =50549a(22) =81790a(23) =132339a(24) =214129a(25) =346468a(26) =560597a(27) =907065a(28) =1467662a(29) =2374727