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%I #7 Nov 05 2017 17:10:20
%S 7,23,28,39,55,71,87,92,103,112,135,151,156,167,183,199,215,220,231,
%T 247,263,279,284,295,311,327,343,348,359,368,391,407,412,423,439,448,
%U 519,535,540,551,567,583,599,604,615,624,647,663
%N Numbers n such that string 1,3 occurs in the base 4 representation of n but not of n-1.
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n,4],{1,3}]>0,1,0],{n,700}],{0,1}][[All,2]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Nov 05 2017 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_