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 A308269 #16 Jan 20 2025 18:40:38 %S A308269 2,7,19,37,67,109,127,157,229,349,397,457,619,727,829,877,1117,1129, %T A308269 1237,1249,1279,1327,1447,1459,1489,1699,1777,1789,1867,1879,1987, %U A308269 1999,2179,2269,2377,2389,2467,2539,2647,2659,2767,2857,2917,3019,3109,3169,3187,3217,3229,3307,3319,3457,3637 %N A308269 Primes p such that 2*p^2 + 2*p - 9 is prime. %C A308269 Primes p such that 4*p^2 is in A308268. %C A308269 Other than 2, all terms == 1 (mod 6). %H A308269 Robert Israel, <a href="/A308269/b308269.txt">Table of n, a(n) for n = 1..10000</a> %e A308269 a(3) = 19 is in the sequence because 19 and 2*19^2 + 2*19 - 9 = 751 are prime. %p A308269 select(p -> isprime(p) and isprime(2*p^2 + 2*p - 9), [2,seq(i,i=7..1000,6)]); %t A308269 Select[Prime[Range[600]],PrimeQ[2#^2+2#-9]&] (* _Harvey P. Dale_, Jun 14 2021 *) %o A308269 (Magma) [p:p in PrimesUpTo(5000)|IsPrime(2*p^2 + 2*p - 9)]; // _Marius A. Burtea_, May 17 2019 %Y A308269 Cf. A308268. %K A308269 nonn %O A308269 1,1 %A A308269 _Robert Israel_, May 17 2019