%I #10 Aug 22 2021 20:50:55
%S 28,53,77,102,126,151,175,196,224,249,273,298,322,347,371,396,420,445,
%T 469,494,518,539,567,592,616,641,665,690,714,739,763,788,812,837,861,
%U 882,910,935,959,984,1008,1033,1057,1082,1106
%N Numbers k such that 0 and 4 occur juxtaposed in the base-7 representation of k but not of k-1.
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n,7],{0,4}]>0 || SequenceCount[ IntegerDigits[n,7],{4,0}]>0,1,0],{n,1200}],{0,1}][[All,2]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Jun 14 2018 *)
%Y Cf. A007093.
%K nonn,base
%O 1,1
%A _Clark Kimberling_