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%I #7 Aug 17 2019 16:45:02
%S 30,79,128,177,210,226,275,324,373,422,471,520,553,569,618,667,716,
%T 765,814,863,896,912,961,1010,1059,1108,1157,1206,1239,1255,1304,1353,
%U 1402,1451,1470,1549,1582,1598,1647,1696,1745,1794
%N Numbers n such that string 4,2 occurs in the base 7 representation of n but not of n-1.
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n,7],{4,2}]>0,1,0],{n,2000}],{0,1}][[All,2]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Aug 17 2019 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_
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