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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A072858 Primes p such that 1/p has a square "period length". 1
2, 3, 5, 17, 101, 163, 257, 577, 883, 1297, 1801, 3137, 3529, 5477, 7057, 7351, 8929, 9397, 11831, 12101, 13457, 13553, 14401, 15361, 15377, 15973, 19841, 20809, 21401, 21601, 23549, 24337, 25601, 29401, 30977, 33301, 33751, 33857, 38237 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..39.

EXAMPLE

The period length of 1/17 = 0.05882352941176470588... is 16 = 4^2, hence 17 is in the sequence. The period length of 1/163 = 81 = 9^2.

PROG

(PARI) (a(n)=if(n<4, n==2, znorder(Mod(10, prime(n))))); for(n=1, 1000, if(issquare(a(n))==1, print1(prime(n), ", "))) /* Thanks to Michael Somos for improvement of the PARI program */

CROSSREFS

Cf. A002371.

Sequence in context: A065952 A308316 A089983 * A276629 A218086 A291049

Adjacent sequences:  A072855 A072856 A072857 * A072859 A072860 A072861

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre, Jul 26 2002

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 October 20 15:46 EDT 2019. Contains 328267 sequences. (Running on oeis4.)