a(n) = greatest integer not found after first n in A026400.

Terms

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