Number of subsets of {1,2,...,n} such that no two elements differ by 2, 4, or 5.

Terms

a(0) =1a(1) =2a(2) =4a(3) =6a(4) =9a(5) =12a(6) =15a(7) =20a(8) =28a(9) =40a(10) =59a(11) =86a(12) =121a(13) =169a(14) =235a(15) =326a(16) =458a(17) =649a(18) =919a(19) =1301a(20) =1837a(21) =2582a(22) =3627a(23) =5101a(24) =7179a(25) =10118a(26) =14272a(27) =20120a(28) =28349a(29) =39930