Number of 4-element nondividing subsets of {1, 2, ..., n}.

Terms

a(0) =1a(1) =2a(2) =3a(3) =6a(4) =10a(5) =21a(6) =32a(7) =49a(8) =65a(9) =101a(10) =150a(11) =224a(12) =305a(13) =413a(14) =525a(15) =707a(16) =908a(17) =1174a(18) =1479a(19) =1871a(20) =2269a(21) =2826a(22) =3396a(23) =4138a(24) =4967a(25) =5991a(26) =6917a(27) =8244a(28) =9673a(29) =11328