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%I #7 Oct 24 2017 17:47:39
%S 8,56,106,155,204,253,302,351,392,449,498,547,596,645,694,742,792,841,
%T 890,939,988,1037,1085,1135,1184,1233,1282,1331,1380,1428,1478,1527,
%U 1576,1625,1674,1723,1771,1821,1870,1919,1968
%N Numbers n such that string 1,1 occurs in the base 7 representation of n but not of n-1.
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n,7],{1,1}]>0,1,0],{n,2000}],{0,1}][[All,2]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Oct 24 2017 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_