login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A061075 Greatest prime number p(n) with decimal fraction period of length n. 6
3, 11, 37, 101, 271, 13, 4649, 137, 333667, 9091, 513239, 9901, 265371653, 909091, 2906161, 5882353, 5363222357, 52579, 1111111111111111111, 27961, 10838689, 8779, 11111111111111111111111, 99990001, 182521213001, 1058313049 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Ray Chandler, Table of n, a(n) for n = 1..322

Makoto Kamada, Factorizations of Phi_n(10)

Index entries for sequences related to decimal expansion of 1/n

FORMULA

a(n) = A006530(A019328(n)). - Ray Chandler, May 10 2017

EXAMPLE

1/271 = 0.0036900369, period of n=5 for p(5)=271.

MATHEMATICA

a[n_] := Cyclotomic[n, 10] // FactorInteger // Last // First; Table[a[n], {n, 1, 26}] (* Jean-Fran├žois Alcover, Aug 05 2013, after Pari *)

PROG

(PARI) a(n) = my(p); if(n<1, 0, p=factor(polcyclo(n, 10))[, 1]; p[#p])

CROSSREFS

Cf. A003020, A005422, A006530, A007138, A019328.

Sequence in context: A007138 A046107 A243110 * A005422 A040017 A007615

Adjacent sequences:  A061072 A061073 A061074 * A061076 A061077 A061078

KEYWORD

nonn,nice,base

AUTHOR

Heiner Muller-Merbach (hmm(AT)sozwi.uni-kl.de), May 29 2001

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 June 1 13:11 EDT 2020. Contains 334762 sequences. (Running on oeis4.)