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Numbers n such that string 7,4 occurs in the base 10 representation of n but not of n+1.
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%I #7 Dec 09 2022 12:54:27

%S 74,174,274,374,474,574,674,749,774,874,974,1074,1174,1274,1374,1474,

%T 1574,1674,1749,1774,1874,1974,2074,2174,2274,2374,2474,2574,2674,

%U 2749,2774,2874,2974,3074,3174,3274,3374,3474,3574

%N Numbers n such that string 7,4 occurs in the base 10 representation of n but not of n+1.

%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n],{7,4}]>0,1,0],{n,4000}],{1,0}][[All,1]] (* _Harvey P. Dale_, Dec 09 2022 *)

%K nonn,base

%O 1,1

%A _Clark Kimberling_