Arises in enumerating Huffman codes, compact trees, and sums of unit fractions.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =4a(5) =8a(6) =16a(7) =32a(8) =64a(9) =128a(10) =256a(11) =512a(12) =1023a(13) =2045a(14) =4089a(15) =8176a(16) =16348a(17) =32688a(18) =65360a(19) =130688a(20) =261312a(21) =522496a(22) =1044736a(23) =2088960a(24) =4176896a(25) =8351746a(26) =16699401a(27) =33390622a(28) =66764888a(29) =133497072