%I #6 Apr 08 2018 14:01:58
%S 10,59,70,108,157,206,255,304,353,402,413,451,490,549,598,647,696,745,
%T 756,794,843,892,941,990,1039,1088,1099,1137,1186,1235,1284,1333,1382,
%U 1431,1442,1480,1529,1578,1627,1676,1725,1774
%N Numbers n such that the string 1,3 occurs in the base 7 representation of n but not of n-1.
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n,7],{1,3}]>0,1,0],{n,2000}],{0,1}][[All,2]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Apr 08 2018 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_
%E Definition reworded by _Harvey P. Dale_, Apr 08 2018