

A186635


Primes p such that the decimal expansion of 1/p has a periodic part of odd length.


2



2, 3, 5, 31, 37, 41, 43, 53, 67, 71, 79, 83, 107, 151, 163, 173, 191, 199, 227, 239, 271, 277, 283, 307, 311, 317, 347, 359, 397, 431, 439, 443, 467, 479, 523, 547, 563, 587, 599, 613, 631, 643, 683, 719, 733, 751, 757, 773, 787, 797, 827, 839, 853, 883, 907, 911, 919, 947, 991, 1013, 1031, 1039, 1093, 1123, 1151, 1163, 1187
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OFFSET

1,1


COMMENTS

Interestingly, the initial terms of A040119 (Primes p such that x^4 = 10 has a solution mod p) are identical to the initial terms of this sequence except for 241 which is a term of A040119 but not of A186635. [John W. Layman, Feb 25 2011]
There are many numbers in A040119 that are not here: 241, 641, 769, 809, 1009, 1409, 1601, 1721....  T. D. Noe, Feb 25 2011


LINKS

Table of n, a(n) for n=1..67.


MAPLE

Ax := proc(n) local st:
st := ithprime(n):
if (modp(numtheory[order](10, st), 2) <> 0) then
RETURN(st)
fi: end: seq(Ax(n), n=1..200);


MATHEMATICA

Union[{2, 5}, Select[Prime[Range[200]], OddQ[Length[RealDigits[1/#][[1, 1]]]] &]]


CROSSREFS

Cf. A002371, A048595, A028416, A040119.
Sequence in context: A090475 A060301 A040119 * A265807 A106308 A036797
Adjacent sequences: A186632 A186633 A186634 * A186636 A186637 A186638


KEYWORD

nonn,base


AUTHOR

Jani Melik, Feb 24 2011


STATUS

approved



