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

Terms

a(0) =1a(1) =1a(2) =2a(3) =2a(4) =4a(5) =4a(6) =9a(7) =11a(8) =24a(9) =38a(10) =75a(11) =131a(12) =263a(13) =476a(14) =928a(15) =1750a(16) =3386a(17) =6439a(18) =12455a(19) =23853a(20) =46097a(21) =88709a(22) =171471a(23) =330939a(24) =640472a(25) =1238755a(26) =2400154a(27) =4650857a(28) =9022792a(29) =17510820