Number of subsets of {1, ..., n} that are double-free or sum-free.

Terms

a(0) =1a(1) =2a(2) =4a(3) =7a(4) =14a(5) =26a(6) =43a(7) =79a(8) =137a(9) =246a(10) =398a(11) =733a(12) =1237a(13) =2314a(14) =3586a(15) =6730a(16) =11051a(17) =21096a(18) =31985a(19) =61654a(20) =102730a(21) =199555a(22) =301062a(23) =589746a(24) =942876a(25) =1858881a(26) =2793703a(27) =5524251a(28) =9193512a(29) =18256867