a(n) is the number of sparse rulers of length n where the length of the first segment is unique.

Terms

a(0) =0a(1) =1a(2) =1a(3) =3a(4) =4a(5) =8a(6) =14a(7) =26a(8) =46a(9) =85a(10) =155a(11) =286a(12) =528a(13) =980a(14) =1824a(15) =3410a(16) =6392a(17) =12022a(18) =22675a(19) =42885a(20) =81312a(21) =154540a(22) =294362a(23) =561849a(24) =1074463a(25) =2058462a(26) =3950220a(27) =7592403a(28) =14614105a(29) =28168227