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 A105877 #16 Nov 06 2024 04:58:09 %S A105877 2,11,17,19,37,53,59,73,79,97,113,131,137,139,151,157,173,179,193,197, %T A105877 233,239,257,277,293,311,317,331,353,359,373,397,419,431,433,439,479, %U A105877 491,499,557,571,577,593,599,613,617,619,653,659,673,677,719,751,757,773,797,811 %N A105877 Primes for which -5 is a primitive root. %C A105877 Conjecture: the penultimate digit of a(n) is always odd. This characteristic seems to be proper of primes for which -5*n^2 is a primitive root. - _Davide Rotondo_, Oct 26 2024 %C A105877 For any n > 1, a(n) == 11, 13, 17, or 19 (mod 20), which implies the conjecture above. - _Max Alekseyev_, Nov 01 2024 %H A105877 Vincenzo Librandi, <a href="/A105877/b105877.txt">Table of n, a(n) for n = 1..1000</a> %H A105877 <a href="/index/Pri#primes_root">Index entries for primes by primitive root</a> %t A105877 pr=-5; Select[Prime[Range[200]], MultiplicativeOrder[pr, # ] == #-1 &] %K A105877 nonn %O A105877 1,1 %A A105877 _N. J. A. Sloane_, Apr 24 2005