Number of subsets of {1,2,...,n} such that no two elements differ by 1, 3, or 4.

Terms

a(0) =1a(1) =2a(2) =3a(3) =5a(4) =7a(5) =9a(6) =12a(7) =16a(8) =23a(9) =33a(10) =47a(11) =66a(12) =91a(13) =126a(14) =175a(15) =245a(16) =344a(17) =482a(18) =674a(19) =940a(20) =1311a(21) =1830a(22) =2557a(23) =3575a(24) =4997a(25) =6982a(26) =9752a(27) =13620a(28) =19025a(29) =26579