%I #9 May 02 2020 16:50:10
%S 78,178,278,378,478,578,678,778,789,878,978,1078,1178,1278,1378,1478,
%T 1578,1678,1778,1789,1878,1978,2078,2178,2278,2378,2478,2578,2678,
%U 2778,2789,2878,2978,3078,3178,3278,3378,3478,3578
%N Numbers n such that string 7,8 occurs in the base 10 representation of n but not of n+1.
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n],{7,8}]>0,1,0],{n,3600}],{1,0}][[All,1]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, May 02 2020 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_