Numbers k such that string 1,2 occurs in the base 9 representation of k but not of k+1.

Terms

a(0) =11a(1) =92a(2) =107a(3) =173a(4) =254a(5) =335a(6) =416a(7) =497a(8) =578a(9) =659a(10) =740a(11) =821a(12) =836a(13) =971a(14) =983a(15) =1064a(16) =1145a(17) =1226a(18) =1307a(19) =1388a(20) =1469a(21) =1550a(22) =1565a(23) =1631a(24) =1712a(25) =1793a(26) =1874a(27) =1955a(28) =2036a(29) =2117