Number of compositions of n when each odd part can be of two kinds.

Terms

a(0) =1a(1) =2a(2) =5a(3) =14a(4) =38a(5) =104a(6) =284a(7) =776a(8) =2120a(9) =5792a(10) =15824a(11) =43232a(12) =118112a(13) =322688a(14) =881600a(15) =2408576a(16) =6580352a(17) =17977856a(18) =49116416a(19) =134188544a(20) =366609920a(21) =1001596928a(22) =2736413696a(23) =7476021248a(24) =20424869888a(25) =55801782272a(26) =152453304320