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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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified November 16 17:39 EST 2018. Contains 317275 sequences. (Running on oeis4.)