Number of subsets of {1..n} containing all of their own first differences.

Terms

a(0) =1a(1) =2a(2) =4a(3) =6a(4) =10a(5) =14a(6) =23a(7) =34a(8) =58a(9) =96a(10) =171a(11) =302a(12) =565a(13) =1041a(14) =1969a(15) =3719a(16) =7105a(17) =13544a(18) =25999a(19) =49852a(20) =95949a(21) =184658a(22) =356129a(23) =687068a(24) =1327540a(25) =2566295a(26) =4966449a(27) =9617306a(28) =18640098a(29) =36150918