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 A277049 #14 Sep 08 2022 08:46:17 %S A277049 3,11,31,59,71,149,179,191,269,359,389,409,479,569,719,839,1019,1039, %T A277049 1091,1319,1439,1609,1619,1699,1759,1861,1949,2039,2099,2239,2309, %U A277049 2459,2579,2621,2749,2819,2879,2909,2939,2999,3119,3229,3449,3461,3581,3709 %N A277049 Primes p such that the multiplicative order of 5 modulo p is prime. %C A277049 Odd primes that divide 5^p-1 for some prime p. - _Robert Israel_, Nov 13 2016 %H A277049 Robert Israel, <a href="/A277049/b277049.txt">Table of n, a(n) for n = 1..10000</a> %p A277049 select(p -> isprime(p) and isprime(numtheory:-order(5,p)), [3,seq(p,p=7..10000,2)]); # _Robert Israel_, Nov 13 2016 %t A277049 Select[Prime@Range@600, PrimeQ@MultiplicativeOrder[5, #] &] %o A277049 (Magma) [p: p in PrimesInInterval(2, 4000) | IsPrime(Modorder(5, p))]; %o A277049 (PARI) is(n) = n!=5 && ispseudoprime(n) && ispseudoprime(znorder(Mod(5, n))) \\ _Felix Fröhlich_, Nov 01 2016 %Y A277049 Cf. A000040, A277048. %K A277049 nonn %O A277049 1,1 %A A277049 _Vincenzo Librandi_, Oct 28 2016