%I #12 Aug 26 2021 03:16:40

%S 23,58,87,122,151,191,215,250,279,314,343,378,407,442,471,506,535,570,

%T 599,634,663,703,727,762,791,826,855,890,919,954,983,1018,1047,1082,

%U 1111,1146,1175,1215,1239,1274,1303,1338,1367

%N Numbers k such that 2 and 7 occur juxtaposed in the base-8 representation of k but not of k+1.

%t s27Q[n_]:=Module[{idn8=IntegerDigits[n,8]},If[SequenceCount[idn8, {2,7}]> 0 ||SequenceCount[idn8,{7,2}]>0,1,0]]; Transpose[ SequencePosition[ Table[ s27Q[n],{n,1400}],{1,0}]][[1]] (* The program uses the SequenceCount and SequencePosition functions from Mathematica version 10 *) (* _Harvey P. Dale_, Oct 10 2015 *)

%Y Cf. A007094.

%K nonn,base

%O 1,1

%A _Clark Kimberling_