The OEIS is supported by the many generous donors to the OEIS Foundation.
%I #7 May 25 2017 12:00:27
%S 50,99,148,197,246,295,344,350,393,442,491,540,589,638,687,693,736,
%T 785,834,883,932,981,1030,1036,1079,1128,1177,1226,1275,1324,1373,
%U 1379,1422,1471,1520,1569,1618,1667,1716,1722,1765,1814
%N Numbers n such that string 0,1 occurs in the base 7 representation of n but not of n-1.
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n,7],{0,1}]>0,1,0],{n,2000}],{0,1}][[All,2]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, May 25 2017 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_