Covering numbers C(n,6,2).

Terms

a(0) =1a(1) =3a(2) =3a(3) =3a(4) =4a(5) =6a(6) =6a(7) =7a(8) =7a(9) =10a(10) =10a(11) =12a(12) =12a(13) =15a(14) =16a(15) =17a(16) =19