%I #7 Oct 17 2015 15:13:55

%S 43,92,141,190,239,288,301,337,386,435,484,533,582,631,644,680,729,

%T 778,827,876,925,974,987,1023,1072,1121,1170,1219,1268,1317,1330,1366,

%U 1415,1464,1513,1562,1611,1660,1673,1709,1758,1807

%N Numbers n such that string 6,1 occurs in the base 7 representation of n but not of n-1.

%t Transpose[SequencePosition[Table[If[SequenceCount[IntegerDigits[n,7],{6,1}]>0,1,0],{n,2000}],{0,1}]][[2]] (* The program uses the SequencePosition and SequenceCount functions from Mathematica version 10 *) (* _Harvey P. Dale_, Oct 17 2015 *)

%K nonn,base

%O 1,1

%A _Clark Kimberling_