%I
%S 53,102,151,200,249,298,347,371,396,445,494,543,592,641,690,714,739,
%T 788,837,886,935,984,1033,1057,1082,1131,1180,1229,1278,1327,1376,
%U 1400,1425,1474,1523,1572,1621,1670,1719,1743,1768,1817
%N Numbers n such that string 0,4 occurs in the base 7 representation of n but not of n1.
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n,7],{0,4}]>0,1,0],{n,2000}],{0,1}][[All,2]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Jun 04 2019 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_
