

A006559


Short period primes: the decimal expansion of 1/p has period less than p1, but greater than zero.
(Formerly M2881)


3



3, 11, 13, 31, 37, 41, 43, 53, 67, 71, 73, 79, 83, 89, 101, 103, 107, 127, 137, 139, 151, 157, 163, 173, 191, 197, 199, 211, 227, 239, 241, 251, 271, 277, 281, 283, 293, 307, 311, 317, 331, 347, 349, 353, 359, 373, 397, 401, 409, 421, 431, 439, 443, 449, 457
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OFFSET

1,1


COMMENTS

Primes 2 and 5 are excluded because 1/2 and 1/5 have no period. Also primes p whose multiplicative order mod p is less than p1.


REFERENCES

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).


LINKS

T. D. Noe, Table of n, a(n) for n = 1..1000
Victor Meally, Letter to N. J. A. Sloane, no date.
Index entries for sequences related to decimal expansion of 1/n


MATHEMATICA

Select[Prime[Range[100]], MultiplicativeOrder[10, #] < #  1 &]


PROG

(PARI) a(n)=gcd(n, 10)==1 && isprime(n) && znorder(Mod(10, n))<n1 \\ Charles R Greathouse IV, Mar 15 2014


CROSSREFS

Cf. A006883.
Sequence in context: A019374 A033680 A032917 * A023248 A199341 A111488
Adjacent sequences: A006556 A006557 A006558 * A006560 A006561 A006562


KEYWORD

nonn,easy,nice,base


AUTHOR

N. J. A. Sloane.


EXTENSIONS

More terms from James A. Sellers, Aug 21 2000


STATUS

approved



