Number of integer compositions of n that are not the first sums of any composition with no 1's.

Terms

a(0) =1a(1) =2a(2) =4a(3) =7a(4) =15a(5) =31a(6) =63a(7) =126a(8) =253a(9) =508a(10) =1019a(11) =2041a(12) =4087a(13) =8179a(14) =16368a(15) =32745a(16) =65508a(17) =131032a(18) =262095a(19) =524219a(20) =1048491a(21) =2097034a(22) =4194158a(23) =8388407a(24) =16776967a(25) =33554091a(26) =67108442a(27) =134217152a(28) =268434744a(29) =536869943