A044482 Numbers k such that the string 4,4 occurs in the base-5 representation of k but not of k+1.

24, 49, 74, 99, 124, 149, 174, 199, 224, 249, 274, 299, 324, 349, 374, 399, 424, 449, 474, 499, 524, 549, 574, 624, 649, 674, 699, 724, 749, 774, 799, 824, 849, 874, 899, 924, 949, 974, 999, 1024, 1049, 1074, 1099, 1124, 1149

Offset: 1

Author

Clark Kimberling

Keywords

• nonn
• base

Comments

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

Examples

			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.
599 is not in the sequence because, although it is 4344 in base 5, 600 is 4400 in base 5.
		

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A008607 (multiples of 25).

Programs

Mathematica

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 *)
SequencePosition[Table[If[SequenceCount[IntegerDigits[n,5],{4,4}]>0,1,0],{n,1200}],{1,0}][[All,1]] (* Harvey P. Dale, Aug 20 2021 *)