A044031 - OEIS

%I #11 Aug 29 2021 01:55:46

%S 56,65,156,165,256,265,356,365,456,465,556,569,659,665,756,765,856,

%T 865,956,965,1056,1065,1156,1165,1256,1265,1356,1365,1456,1465,1556,

%U 1569,1659,1665,1756,1765,1856,1865,1956,1965,2056

%N Numbers k such that 5 and 6 occur juxtaposed in the base-10 representation of k but not of k+1.

%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n],{5,6}]>0 || SequenceCount[ IntegerDigits[n],{6,5}]>0,1,0],{n,2100}],{1,0}][[All,1]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Nov 15 2020 *)

%K nonn,base

%O 1,1

%A _Clark Kimberling_