Binomial coefficients: C(n,k), 1 <= k <= n-1, sorted.

Terms

a(0) =2a(1) =3a(2) =3a(3) =4a(4) =4a(5) =5a(6) =5a(7) =6a(8) =6a(9) =6a(10) =7a(11) =7a(12) =8a(13) =8a(14) =9a(15) =9a(16) =10a(17) =10a(18) =10a(19) =10a(20) =11a(21) =11a(22) =12a(23) =12a(24) =13a(25) =13a(26) =14a(27) =14a(28) =15a(29) =15