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%I #7 Jul 15 2019 17:04:12
%S 64,164,264,364,464,564,649,664,764,864,964,1064,1164,1264,1364,1464,
%T 1564,1649,1664,1764,1864,1964,2064,2164,2264,2364,2464,2564,2649,
%U 2664,2764,2864,2964,3064,3164,3264,3364,3464,3564
%N Numbers n such that string 6,4 occurs in the base 10 representation of n but not of n+1.
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n],{6,4}]>0,1,0],{n,4000}],{1,0}][[All,1]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Jul 15 2019 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_