%I #15 Nov 25 2021 07:32:12
%S 11,25,75,95,139,153,207,217,267,281,331,345,395,409,459,473,523,537,
%T 587,607,651,665,767,779,793,843,857,907,921,971,985,1035,1049,1099,
%U 1119,1163,1177,1231,1241,1291,1305,1355,1369,1419,1433,1483,1497,1547,1561
%N Numbers k such that 1 and 3 occur juxtaposed in the base-8 representation of k but not of k+1.
%H Michael S. Branicky, <a href="/A043940/b043940.txt">Table of n, a(n) for n = 1..10000</a>
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n,8],{1,3}]>0 || SequenceCount[IntegerDigits[n,8],{3,1}]>0,1,0],{n,1400}],{1,0}][[All,1]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Sep 07 2020 *)
%o (Python)
%o def has13or31(n): o = oct(n); return "13" in o or "31" in o
%o def ok(n): return has13or31(n) and not has13or31(n+1)
%o print([k for k in range(1600) if ok(k)]) # _Michael S. Branicky_, Nov 25 2021
%Y Cf. A007094, A043160.
%K nonn,base
%O 1,1
%A _Clark Kimberling_