Covering numbers C(n,4,2).

Terms

a(0) =1a(1) =3a(2) =3a(3) =5a(4) =6a(5) =8a(6) =9a(7) =11a(8) =12a(9) =13a(10) =18a(11) =19a(12) =20a(13) =26a(14) =27a(15) =31a(16) =35a(17) =37a(18) =39a(19) =46a(20) =48a(21) =50a(22) =59a(23) =61a(24) =63a(25) =73a(26) =75a(27) =78a(28) =88a(29) =91