Number of subsets of {1,...,n} not containing {a,a+2,a+4} for any a.

Terms

a(0) =1a(1) =2a(2) =4a(3) =8a(4) =16a(5) =28a(6) =49a(7) =91a(8) =169a(9) =312a(10) =576a(11) =1056a(12) =1936a(13) =3564a(14) =6561a(15) =12069a(16) =22201a(17) =40826a(18) =75076a(19) =138096a(20) =254016a(21) =467208a(22) =859329a(23) =1580535a(24) =2907025a(25) =5346880a(26) =9834496a(27) =18088448a(28) =33269824a(29) =61192712