The OEIS is supported by the many generous donors to the OEIS Foundation.

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

0

`%I #9 Jul 12 2021 12:32:15
`

`%S 11,92,99,173,254,335,416,497,578,659,740,821,828,891,983,1064,1145,
`

`%T 1226,1307,1388,1469,1550,1557,1631,1712,1793,1874,1955,2036,2117,
`

`%U 2198,2279,2286,2360,2441,2522,2603,2684,2765,2846
`

`%N Numbers n such that string 1,2 occurs in the base 9 representation of n but not of n-1.
`

`%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n,9],{1,2}]>0,1,0],{n,2900}],{0,1}][[All,2]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Jul 12 2021 *)
`

`%K nonn,base
`

`%O 1,1
`

`%A _Clark Kimberling_
`