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Numbers n such that string 7,1 occurs in the base 9 representation of n but not of n-1.
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%I #7 Nov 12 2017 08:26:13

%S 64,145,226,307,388,469,550,576,631,712,793,874,955,1036,1117,1198,

%T 1279,1305,1360,1441,1522,1603,1684,1765,1846,1927,2008,2034,2089,

%U 2170,2251,2332,2413,2494,2575,2656,2737,2763,2818

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

%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n,9],{7,1}]>0,1,0],{n,3000}],{0,1}][[All,2]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Nov 12 2017 *)

%K nonn,base

%O 1,1

%A _Clark Kimberling_