A217187 a(n) is the number of digits in the decimal representation of the smallest power of 5 that contains n consecutive identical digits.

1, 8, 35, 67, 88, 760, 1948, 1951, 1955, 1956, 1959, 1960

Offset

1,2

Comments

Number of digits in 5^k is equal to floor(1 + k*log_10(5)).

Links

Table of n, a(n) for n=1..12.

Mathematica

k = 0; Join[{1}, Table[While[d = IntegerDigits[5^k]; prt = Partition[Differences[d], n - 1, 1]; ! MemberQ[prt, Table[0, {n - 1}]], k++]; Length[d], {n, 2, 8}]] (* T. D. Noe, Oct 03 2012 *)
Module[{nn=3000, p5}, p5=5^Range[nn]; Table[IntegerLength[SelectFirst[p5, SequenceCount[ IntegerDigits[ #], PadRight[{}, n, x_]]>0&]], {n, 12}]] (* Harvey P. Dale, Aug 27 2023 *)

Crossrefs

Cf. A215728, A215734.

Sequence in context: A275360 A281147 A373484 * A214725 A136016 A257454

Adjacent sequences: A217184 A217185 A217186 * A217188 A217189 A217190

Keyword

nonn,base

Author

V. Raman, Sep 27 2012

Status

approved