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 A038891 #17 Jul 08 2025 22:26:54 %S A038891 3,5,17,19,31,59,61,67,71,73,79,101,103,107,127,137,149,151,157,167, %T A038891 179,197,211,223,227,229,233,277,307,313,331,349,353,379,383,389,397, %U A038891 431,439,457,461,487,523,541,547 %N A038891 Odd primes p such that 19 is a square mod p. %C A038891 Also, only entries p=1 (mod 4) of the sequence are squares mod 19 (from the quadratic reciprocity law). - _Lekraj Beedassy_, Jul 21 2004 %H A038891 Vincenzo Librandi, <a href="/A038891/b038891.txt">Table of n, a(n) for n = 1..1000</a> %t A038891 Select[Prime[Range[100]], JacobiSymbol[19, #] != -1 &] (* _Vincenzo Librandi_, Sep 07 2012 *) %o A038891 (PARI) isok(p) = (p>2) && isprime(p) && issquare(Mod(19, p)); \\ _Michel Marcus_, Jun 23 2019 %K A038891 nonn %O A038891 1,1 %A A038891 _N. J. A. Sloane_ %E A038891 Name clarified by _Michel Marcus_, Jun 23 2019