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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A104381 Numbers n such that 10^(n-1) == 1 (mod n). 1
1, 3, 7, 9, 11, 13, 17, 19, 23, 29, 31, 33, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 91, 97, 99, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 259, 263 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Superset of the full reptend primes.

LINKS

Table of n, a(n) for n=1..60.

Eric Weisstein's World of Mathematics, Full Reptend Prime

MATHEMATICA

Select[ Range[270], Mod[ PowerMod[10, # - 1, # ] - 1, # ] == 0 &] (* Robert G. Wilson v, Mar 16 2005 *)

Join[{1}, Select[Range[300], PowerMod[10, #-1, #]==1&]] (* Harvey P. Dale, Oct 24 2016 *)

PROG

(PARI) isok(n) = lift(Mod(10, n)^(n-1)) == 1; \\ Michel Marcus, Sep 25 2014

CROSSREFS

Sequence in context: A105585 A080903 A172253 * A136333 A134454 A324695

Adjacent sequences:  A104378 A104379 A104380 * A104382 A104383 A104384

KEYWORD

nonn

AUTHOR

Eric W. Weisstein, Mar 03 2005

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 15 17:24 EDT 2019. Contains 328037 sequences. (Running on oeis4.)