Number of subsets of {1, ..., n} that are not sum-free.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =3a(5) =10a(6) =27a(7) =67a(8) =154a(9) =350a(10) =763a(11) =1638a(12) =3450a(13) =7191a(14) =14831a(15) =30398a(16) =61891a(17) =125557a(18) =253841a(19) =511818a(20) =1029863a(21) =2069341a(22) =4153060a(23) =8327646a(24) =16687483a(25) =33422562a(26) =66916342a(27) =133936603a(28) =268026776a(29) =536277032