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%I #7 Apr 30 2020 16:46:42
%S 15,79,127,143,207,271,335,399,463,527,591,639,655,719,783,847,911,
%T 1023,1039,1103,1151,1167,1231,1295,1359,1423,1487,1551,1615,1663,
%U 1679,1743,1807,1871,1935,1999,2063,2127,2175,2191,2255
%N Numbers n such that string 1,7 occurs in the base 8 representation of n but not of n+1.
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n,8],{1,7}]>0,1,0],{n,2500}],{1,0}][[All,1]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Apr 30 2020 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_