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 A090866 #32 Sep 08 2022 08:45:12
%S A090866 13,29,53,149,173,269,293,317,389,509,557,653,773,797,1109,1229,1493,
%T A090866 1637,1733,1949,1997,2309,2477,2693,2837,2909,2957,3413,3533,3677,
%U A090866 3989,4133,4157,4253,4349,4373,4493,4517,5189,5309,5693,5717,5813,6173,6197
%N A090866 Primes p == 1 (mod 4) such that (p-1)/4 is prime.
%C A090866 Same as Chebyshev's subsequence of the primes with primitive root 2, because Chebyshev showed that 2 is a primitive root of all primes p = 4*q+1 with q prime. If the sequence is infinite, then Artin's conjecture ("every nonsquare positive integer n is a primitive root of infinitely many primes q") is true for n = 2. - _Jonathan Sondow_, Feb 04 2013
%D A090866 Albert H. Beiler: Recreations in the theory of numbers. New York: Dover, (2nd ed.) 1966, p. 102, nr. 5.
%D A090866 P. L. Chebyshev, Theory of congruences. Elements of number theory, Chelsea, 1972, p. 306.
%H A090866 G. C. Greubel, <a href="/A090866/b090866.txt">Table of n, a(n) for n = 1..10000</a>
%H A090866 <a href="/index/Ar#Artin">Index entries for sequences related to Artin's conjecture</a>
%F A090866 a(n) = 4*A023212(n) + 1.
%t A090866 Select[Prime[Range[1000]], Mod[#, 4]==1 && PrimeQ[(#-1)/4] &] (* _G. C. Greubel_, Feb 08 2019 *)
%o A090866 (Magma) f:=[n: n in [1..2000] | IsPrime(n) and IsPrime(4*n+1)]; [4*f[n] + 1: n in [1..50]]; // _G. C. Greubel_, Feb 08 2019
%o A090866 (PARI) isok(p) = isprime(p) && !frac(q=(p-1)/4) && isprime(q); \\ _Michel Marcus_, Feb 09 2019
%Y A090866 Cf. A001122, A005385, A005596, A023212, A221981, A222008.
%K A090866 nonn
%O A090866 1,1
%A A090866 _Benoit Cloitre_, Feb 12 2004