%I #7 May 11 2021 17:33:44
%S 42,142,242,342,429,442,542,642,742,842,942,1042,1142,1242,1342,1429,
%T 1442,1542,1642,1742,1842,1942,2042,2142,2242,2342,2429,2442,2542,
%U 2642,2742,2842,2942,3042,3142,3242,3342,3429,3442
%N Numbers n such that string 4,2 occurs in the base 10 representation of n but not of n+1.
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n],{4,2}]>0,1,0],{n,3500}],{1,0}][[All,1]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, May 11 2021 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_