%I #29 Jan 28 2022 07:44:24
%S 24,49,74,99,124,149,174,199,224,249,274,299,324,349,374,399,424,449,
%T 474,499,524,549,574,624,649,674,699,724,749,774,799,824,849,874,899,
%U 924,949,974,999,1024,1049,1074,1099,1124,1149
%N Numbers k such that the string 4,4 occurs in the base-5 representation of k but not of k+1.
%C a(n)+1 is divisible by 25 because the string 4,4 must be at the lower end of the base-5 representation. - _Joerg Arndt_, Feb 13 2012
%H Vincenzo Librandi, <a href="/A044482/b044482.txt">Table of n, a(n) for n = 1..1000</a>
%e 49 is in the sequence because its base-5 representation, 144, includes 44 as a substring, but the base-5 representation of 50, 200, does not.
%e 599 is not in the sequence because, although it is 4344 in base 5, 600 is 4400 in base 5.
%t f[n_]:= Length[StringPosition[ToString[FromDigits[IntegerDigits[n,5]]],"44",1]]; Select[Table[n,{n,2000}],f[#]>0&&f[#+1] == 0&] (* _Vincenzo Librandi_, Feb 12 2012 *)
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n,5],{4,4}]>0,1,0],{n,1200}],{1,0}][[All,1]] (* _Harvey P. Dale_, Aug 20 2021 *)
%Y Cf. A008607 (multiples of 25).
%K nonn,base
%O 1,1
%A _Clark Kimberling_
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