%I #7 Oct 07 2018 15:33:35
%S 45,94,143,192,241,290,321,339,388,437,486,535,584,633,664,682,731,
%T 780,829,878,927,976,1007,1025,1074,1123,1172,1221,1270,1319,1350,
%U 1368,1417,1466,1515,1564,1613,1662,1693,1711,1760,1809
%N Numbers n such that string 6,3 occurs in the base 7 representation of n but not of n+1.
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n,7],{6,3}]>0,1,0],{n,2000}],{1,0}][[All,1]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Oct 07 2018 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_
