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%I M2881 #33 Dec 18 2021 20:52:46
%S 3,11,13,31,37,41,43,53,67,71,73,79,83,89,101,103,107,127,137,139,151,
%T 157,163,173,191,197,199,211,227,239,241,251,271,277,281,283,293,307,
%U 311,317,331,347,349,353,359,373,397,401,409,421,431,439,443,449,457
%N Short period primes: the decimal expansion of 1/p has period less than p-1, but greater than zero.
%C 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 p-1.
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H T. D. Noe, <a href="/A006559/b006559.txt">Table of n, a(n) for n = 1..1000</a>
%H Victor Meally, <a href="/A006556/a006556.pdf">Letter to N. J. A. Sloane</a>, no date.
%H <a href="/index/1#1overn">Index entries for sequences related to decimal expansion of 1/n</a>
%t Select[Prime[Range[100]], MultiplicativeOrder[10, #] < # - 1 &]
%o (PARI) a(n)=gcd(n,10)==1 && isprime(n) && znorder(Mod(10,n))<n-1 \\ _Charles R Greathouse IV_, Mar 15 2014
%Y Cf. A006883.
%K nonn,easy,nice,base
%O 1,1
%A _N. J. A. Sloane_
%E More terms from _James A. Sellers_, Aug 21 2000
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