Number of subsets of {1..n} not containing all of their own first differences.

Terms

a(0) =0a(1) =0a(2) =0a(3) =2a(4) =6a(5) =18a(6) =41a(7) =94a(8) =198a(9) =416a(10) =853a(11) =1746a(12) =3531a(13) =7151a(14) =14415a(15) =29049a(16) =58431a(17) =117528a(18) =236145a(19) =474436a(20) =952627a(21) =1912494a(22) =3838175a(23) =7701540a(24) =15449676a(25) =30988137a(26) =62142415a(27) =124600422a(28) =249795358a(29) =500719994