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%I #7 Oct 27 2019 11:58:41
%S 25,125,225,250,325,425,525,625,725,825,925,1025,1125,1225,1250,1325,
%T 1425,1525,1625,1725,1825,1925,2025,2125,2225,2250,2325,2425,2500,
%U 2625,2725,2825,2925,3025,3125,3225,3250,3325,3425
%N Numbers n such that string 2,5 occurs in the base 10 representation of n but not of n-1.
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n],{2,5}]>0,1,0],{n,3500}],{0,1}][[All,2]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Oct 27 2019 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_