A217189 a(n) is the number of digits in the decimal representation of the smallest power of 7 that contains n consecutive identical digits.

1, 6, 27, 61, 146, 148, 1658, 5220, 28595, 51790

Offset

1,2

Comments

Number of digits in 7^k is equal to floor(1 + k*log_10(7)).

Links

Table of n, a(n) for n=1..10.

Mathematica

k = 0; Join[{1}, Table[While[d = IntegerDigits[7^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 *)

Crossrefs

Cf. A215730, A215736.

Sequence in context: A273578 A012720 A012365 * A363696 A167469 A190623

Adjacent sequences: A217186 A217187 A217188 * A217190 A217191 A217192

Keyword

nonn,base

Author

V. Raman, Sep 27 2012

Extensions

a(10) added by V. Raman, Nov 23 2013

Status

approved