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 A167800 #7 Jan 04 2025 00:37:59 %S A167800 3,7,9,11,19,23,27,47,49,59,67,71,79,81,83,103,107,121,131,139,163, %T A167800 167,179,191,199,211,227,239,243,263,271,311,343,347,359,361,367,379, %U A167800 383,419,443,463,467,479,487,491,503,523,529,547,563,587,599,607,619,647 %N A167800 Numbers with primitive root -4. %H A167800 Vincenzo Librandi, <a href="/A167800/b167800.txt">Table of n, a(n) for n = 1..1000</a> %t A167800 pr=-4; Select[Range[2,2000], MultiplicativeOrder[pr,# ] == EulerPhi[ # ] &] %o A167800 (PARI) is(n)=if(n%2==0, return(0)); my(p=eulerphi(n)); znorder(Mod(-4, n), p)==p \\ _Charles R Greathouse IV_, Jan 04 2025 %Y A167800 Cf. A105876 (primes with primitive root -4) %K A167800 nonn %O A167800 1,1 %A A167800 _T. D. Noe_, Nov 12 2009