

A217189


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


0




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 * A167469 A190623 A305158
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



