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Numbers n such that string 4,6 occurs in the base 10 representation of n but not of n-1.
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%I #7 Jul 15 2019 17:47:31

%S 46,146,246,346,446,460,546,646,746,846,946,1046,1146,1246,1346,1446,

%T 1460,1546,1646,1746,1846,1946,2046,2146,2246,2346,2446,2460,2546,

%U 2646,2746,2846,2946,3046,3146,3246,3346,3446,3460

%N Numbers n such that string 4,6 occurs in the base 10 representation of n but not of n-1.

%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n],{4,6}]>0,1,0],{n,4000}],{0,1}][[All,2]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Jul 15 2019 *)

%K nonn,base

%O 1,1

%A _Clark Kimberling_