%I #7 Mar 25 2021 14:00:13
%S 73,173,273,373,473,573,673,730,773,873,973,1073,1173,1273,1373,1473,
%T 1573,1673,1730,1773,1873,1973,2073,2173,2273,2373,2473,2573,2673,
%U 2730,2773,2873,2973,3073,3173,3273,3373,3473,3573
%N Numbers n such that string 7,3 occurs in the base 10 representation of n but not of n-1.
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n],{7,3}]>0,1,0],{n,4000}],{0,1}][[All,2]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Mar 25 2021 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_