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%I #7 Jan 23 2021 15:15:14
%S 7,47,79,115,151,187,223,287,295,331,367,403,439,479,511,547,583,619,
%T 655,695,727,763,799,835,871,911,943,979,1015,1051,1087,1127,1159,
%U 1195,1231,1267,1303,1343,1375,1411,1447,1483,1727
%N Numbers n such that string 1,1 occurs in the base 6 representation of n but not of n+1.
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n,6],{1,1}]>0,1,0],{n,1800}],{1,0}][[All,1]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Jan 23 2021 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_