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Numbers n such that string 7,2 occurs in the base 10 representation of n but not of n-1.
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%I #7 Apr 10 2023 10:17:33

%S 72,172,272,372,472,572,672,720,772,872,972,1072,1172,1272,1372,1472,

%T 1572,1672,1720,1772,1872,1972,2072,2172,2272,2372,2472,2572,2672,

%U 2720,2772,2872,2972,3072,3172,3272,3372,3472,3572

%N Numbers n such that string 7,2 occurs in the base 10 representation of n but not of n-1.

%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n],{7,2}]>0,1,0],{n,4000}],{0,1}][[;;,2]] (* _Harvey P. Dale_, Apr 10 2023 *)

%K nonn,base

%O 1,1

%A _Clark Kimberling_