Numbers k such that 1 and 2 occur juxtaposed in the base-9 representation of k but not of k-1.

Terms

a(0) =11a(1) =19a(2) =92a(3) =99a(4) =171a(5) =181a(6) =254a(7) =262a(8) =335a(9) =343a(10) =416a(11) =424a(12) =497a(13) =505a(14) =578a(15) =586a(16) =659a(17) =667a(18) =740a(19) =748a(20) =821a(21) =828a(22) =891a(23) =983a(24) =991a(25) =1064a(26) =1072a(27) =1145a(28) =1153a(29) =1226