login
This site is supported by donations to The OEIS Foundation.

 

Logo

Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing.
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A120100 Integers n for which the period of the decimal expansion of 1/n is 6. 1
7, 13, 14, 21, 26, 28, 35, 39, 42, 52, 56, 63, 65, 70, 77, 78, 84, 91, 104, 105, 112, 117, 126, 130, 140, 143, 154, 156, 168, 175, 182, 189, 195, 208, 210, 224, 231, 234, 252, 259, 260, 273, 280, 286, 297, 308, 312, 315, 325, 336, 350, 351, 364, 378, 385, 390 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The initial terms in the sequence are multiples of either 7 or 13, but the sequence is not exclusively so. a(45) = 297 whose factors include neither 7 nor 13. Next is a(57) = 407 whose factors are 11 and 37.

LINKS

Table of n, a(n) for n=1..56.

EXAMPLE

a(1) = 7 because 1/7 = 0.142857142857142857+, whose repeating decimal (142857) is 6 digits long.

a(57) = 407 because 1/407 = 0.0024570024570024+, whose repeating decimal (002457) is 6 digits long.

MATHEMATICA

Transpose[Select[Table[{n, Length[RealDigits[1/n][[1, -1]]]}, {n, 500}], #[[2]]==6&]][[1]] (* Harvey P. Dale, Dec 04 2010 *)

CROSSREFS

Sequence in context: A232437 A275201 A274558 * A308525 A104217 A269163

Adjacent sequences:  A120097 A120098 A120099 * A120101 A120102 A120103

KEYWORD

nonn,base

AUTHOR

Gil Broussard, Aug 15 2006

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 7 00:16 EST 2019. Contains 329812 sequences. (Running on oeis4.)