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Numbers n such that string 7,4 occurs in the base 9 representation of n but not of n+1.
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%I #7 Mar 13 2016 13:27:04

%S 67,148,229,310,391,472,553,611,634,715,796,877,958,1039,1120,1201,

%T 1282,1340,1363,1444,1525,1606,1687,1768,1849,1930,2011,2069,2092,

%U 2173,2254,2335,2416,2497,2578,2659,2740,2798,2821

%N Numbers n such that string 7,4 occurs in the base 9 representation of n but not of n+1.

%t Transpose[SequencePosition[Table[If[SequenceCount[IntegerDigits[n,9],{7,4}]>0,1,0],{n,3000}],{1,0}]][[1]] (* The program uses the SequencePosition and SequenceCount functions from Mathematica version 10 *) (* _Harvey P. Dale_, Mar 13 2016 *)

%K nonn,base

%O 1,1

%A _Clark Kimberling_