

A001913


Full reptend primes: primes with primitive root 10.
(Formerly M4353 N1823)


46



7, 17, 19, 23, 29, 47, 59, 61, 97, 109, 113, 131, 149, 167, 179, 181, 193, 223, 229, 233, 257, 263, 269, 313, 337, 367, 379, 383, 389, 419, 433, 461, 487, 491, 499, 503, 509, 541, 571, 577, 593, 619, 647, 659, 701, 709, 727, 743, 811, 821, 823, 857, 863, 887, 937, 941
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OFFSET

1,1


COMMENTS

Primes p such that the decimal expansion of 1/p has period p1, which is the greatest period possible for any integer.
Primes p such that the corresponding entry in A002371 is p1.
Pieter Moree writes (Oct 20 2004): Assuming the Generalized Riemann Hypothesis it can be shown that the density of primes p such that a prescribed integer g has order (p1)/t, with t fixed exists and, moreover, it can be computed. This density will be a rational number times the so called Artin constant. For 2 and 10 the density of primitive roots is A, the Artin constant itself.
R. K. Guy writes (Oct 20 2004): MR 2004j:11141 speaks of the unearthing by Lenstra & Stevenhagen of correspondence concerning the density of this sequence between the Lehmers & Artin.
Also called long period primes, long primes or maximal period primes.
The base 10 cyclic numbers A180340, (b^(p1)  1) / p, with b = 10, are obtained from the full reptend primes p.  Daniel Forgues, Dec 17 2012
The number of terms < 10^n: A086018(n)  Robert G. Wilson v, Aug 18 2014


REFERENCES

M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 864.
Albert H. Beiler, Recreations in the Theory of Numbers, 2nd ed. New York: Dover, 1966, pages 65, 309.
John H. Conway and R. K. Guy, The Book of Numbers, Copernicus Press, p. 161.
C. F. Gauss, Disquisitiones Arithmeticae, Yale, 1965; see p. 380.
G. H. Hardy and E. M. Wright, An Introduction to the Theory of Numbers. 3rd ed., Oxford Univ. Press, 1954, p. 115.
M. Kraitchik, Recherches sur la ThÃ©orie des Nombres. GauthiersVillars, Paris, Vol. 1, 1924, Vol. 2, 1929, see Vol. 1, p. 61.
H. Rademacher and O. Toeplitz, Von Zahlen und Figuren (Springer 1930, reprinted 1968), Ch. 19, 'Die periodischen Dezimalbrueche'.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).


LINKS

T. D. Noe and Robert Israel, Table of n, a(n) for n = 1..10000 (first 1000 terms from T. D. Noe)
M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy].
B. Chanco, Full Reptend Prime
L. J. Goldstein, Density questions in algebraic number theory, Amer. Math. Monthly, 78 (1971), 342349.
Pieter Moree, Artin's primitive root conjecture  a survey
OEIS Wiki, Full reptend primes
Eric Weisstein's World of Mathematics, Cyclic Number.
Eric Weisstein's World of Mathematics, Decimal Expansion.
Eric Weisstein's World of Mathematics, Full Reptend Prime.
D. Williams, Primitive Roots (Check)
Chai Wah Wu, Pigeonholes and repunits, Amer. Math. Monthly, 121 (2014), 529533.
Index entries for primes by primitive root
Index entries for sequences related to decimal expansion of 1/n


EXAMPLE

7 is in the sequence because 1/7 = 0.142857142857... and the length of the period = 71 = 6.


MAPLE

A001913 := proc(n) local st, period:
st := ithprime(n):
period := numtheory[order](10, st):
if (st1 = period) then
RETURN(st):
fi: end: seq(A001913(n), n=1..200); #  Jani Melik, Feb 25 2011


MATHEMATICA

pr=10; Select[Prime[Range[200]], MultiplicativeOrder[pr, # ] == #1 &]


PROG

(PARI) forprime(p=7, 1e3, if(znorder(Mod(10, p))+1==p, print1(p", "))) \\ Charles R Greathouse IV, Feb 27 2011
(PARI) is(n)=Mod(10, n)^(n\2)==1 && isprime(n) && znorder(Mod(10, n))+1==n \\ Charles R Greathouse IV, Oct 24 2013


CROSSREFS

Apart from initial term, identical to A006883.
Other definitions of cyclic numbers: A003277, A001914, A180340.
Cf. A005596, A001122, A048296.
Sequence in context: A101240 A191070 A167797 * A071845 A084704 A198032
Adjacent sequences: A001910 A001911 A001912 * A001914 A001915 A001916


KEYWORD

nonn,easy,nice


AUTHOR

N. J. A. Sloane.


STATUS

approved



