Number of integer compositions of n that are not the first sums of any composition.

Terms

a(0) =1a(1) =1a(2) =3a(3) =6a(4) =13a(5) =27a(6) =57a(7) =116a(8) =240a(9) =485a(10) =988a(11) =1989a(12) =4017a(13) =8065a(14) =16214a(15) =32498a(16) =65175a(17) =130504a(18) =261385a(19) =523103a(20) =1046993a(21) =2094696a(22) =4191024a(23) =8383545a(24) =16770456a(25) =33544041a(26) =67094993a(27) =134196481a(28) =268407098a(29) =536827602