This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A072859 #25 Apr 29 2024 09:30:10 %S A072859 11,37,41,53,79,83,107,173,227,239,271,317,347,359,467,479,563,587, %T A072859 643,719,733,773,797,839,907,1031,1187,1231,1283,1307,1319,1439,1493, %U A072859 1523,1627,1637,1879,1907,1987,2027,2039,2467,2477,2677,2791,2837,2879,2963 %N A072859 Primes p for which the period of 1/p is prime. %C A072859 Primes p such that the multiplicative order of 10 (mod p) is prime. - _Joerg Arndt_, Oct 26 2014 %C A072859 Together with 3, complement in primes of A249330. - _Arkadiusz Wesolowski_, Oct 25 2014 %H A072859 Ray Chandler, <a href="/A072859/b072859.txt">Table of n, a(n) for n = 1..10000</a> %e A072859 1/37 = 0. 027 027 ... with period = 3, hence 37 is in the sequence. %t A072859 Select[Prime[Range[500]],PrimeQ[MultiplicativeOrder[10,#]]&] (* _Ray Chandler_, Oct 31 2011 *) %o A072859 (PARI) f(n)=if(n<4,n==2,znorder(Mod(10, prime(n)))); %o A072859 for(n=1,100,if(isprime(f(n))==1,print1(prime(n),", "))) %Y A072859 Cf. A002371, A249330. %K A072859 base,easy,nonn %O A072859 1,1 %A A072859 _Benoit Cloitre_, Jul 26 2002