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Numbers n such that string 7,5 occurs in the base 10 representation of n but not of n+1.
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%I #7 Dec 29 2018 15:26:20

%S 75,175,275,375,475,575,675,759,775,875,975,1075,1175,1275,1375,1475,

%T 1575,1675,1759,1775,1875,1975,2075,2175,2275,2375,2475,2575,2675,

%U 2759,2775,2875,2975,3075,3175,3275,3375,3475,3575

%N Numbers n such that string 7,5 occurs in the base 10 representation of n but not of n+1.

%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n],{7,5}]>0,1,0],{n,3600}],{1,0}][[All,1]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Dec 29 2018 *)

%K nonn,base

%O 1,1

%A _Clark Kimberling_