Number of strings of n 2's and 3's having a tail of length 1.

Terms

a(0) =0a(1) =1a(2) =2a(3) =5a(4) =9a(5) =18a(6) =34a(7) =71a(8) =139a(9) =280a(10) =555a(11) =1119a(12) =2228a(13) =4462a(14) =8907a(15) =17835a(16) =35634a(17) =71288a(18) =142507a(19) =285077a(20) =570013a(21) =1140102a(22) =2279924a(23) =4560040a(24) =9119516a(25) =18239335a(26) =36477548a(27) =72955801a(28) =145909351a(29) =291819915