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%I #13 Aug 28 2021 02:50:13
%S 19,91,119,199,219,291,319,391,419,491,519,591,619,691,719,791,819,
%T 891,919,991,1019,1091,1119,1199,1219,1291,1319,1391,1419,1491,1519,
%U 1591,1619,1691,1719,1791,1819,1891,1999,2019,2091
%N Numbers k such that 1 and 9 occur juxtaposed in the base-10 representation of k but not of k+1.
%H Michael De Vlieger, <a href="/A044012/b044012.txt">Table of n, a(n) for n = 1..10000</a>
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n],{1,9}]>0 || SequenceCount[ IntegerDigits[n],{9,1}]>0,1,0],{n,2100}],{1,0}][[All,1]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Apr 12 2019 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_
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