%I #10 Jan 28 2020 01:16:53
%S 46,95,144,193,242,291,328,340,389,438,487,536,585,634,671,683,732,
%T 781,830,879,928,977,1014,1026,1075,1124,1173,1222,1271,1320,1357,
%U 1369,1418,1467,1516,1565,1614,1663,1700,1712,1761,1810
%N Numbers n such that string 6,4 occurs in the base 7 representation of n but not of n+1.
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n,7],{6,4}]>0,1,0],{n,2000}],{1,0}][[All,1]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Dec 10 2019 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_