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%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_