Number of subsets of {1..n} with elements disjoint from first differences of elements.

Terms

a(0) =1a(1) =2a(2) =3a(3) =6a(4) =10a(5) =18a(6) =30a(7) =54a(8) =92a(9) =167a(10) =290a(11) =525a(12) =935a(13) =1704a(14) =3082a(15) =5664a(16) =10386a(17) =19249a(18) =35701a(19) =66702a(20) =124855a(21) =234969a(22) =443174a(23) =839254a(24) =1592925a(25) =3032757a(26) =5786153a(27) =11066413a(28) =21204855a(29) =40712426