A044387 - OEIS

%I #7 Aug 13 2021 17:32:08

%S 55,155,255,355,455,550,655,755,855,955,1055,1155,1255,1355,1455,1550,

%T 1655,1755,1855,1955,2055,2155,2255,2355,2455,2550,2655,2755,2855,

%U 2955,3055,3155,3255,3355,3455,3550,3655,3755,3855

%N Numbers n such that string 5,5 occurs in the base 10 representation of n but not of n-1.

%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n],{5,5}]>0,1,0],{n,4000}],{0,1}][[All,2]] (* _Harvey P. Dale_, Aug 13 2021 *)

%K nonn,base

%O 1,1

%A _Clark Kimberling_