%I #7 Jun 20 2021 20:06:05
%S 71,171,271,371,471,571,671,719,771,871,971,1071,1171,1271,1371,1471,
%T 1571,1671,1719,1771,1871,1971,2071,2171,2271,2371,2471,2571,2671,
%U 2719,2771,2871,2971,3071,3171,3271,3371,3471,3571
%N Numbers n such that string 7,1 occurs in the base 10 representation of n but not of n+1.
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n],{7,1}]>0,1,0],{n,4000}],{1,0}][[All,1]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Jun 20 2021 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_