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 A338476 #13 Jan 13 2023 18:39:21 %S A338476 397,3581,6367,9949,14327,19501,25471,32237,39799,48157,67261,78007, %T A338476 115021,128951,143677,159199,192631,229247,248749,290141,312031, %U A338476 334717,433421,460087,544861,574711,735901,770527,842167,879181,1035197,1076191,1160567,1203949,1338871,1385437,1432799,1786621 %N A338476 Primes of the form 398*x^2-1. %C A338476 There are 414 such primes for 1 <= x <= 1000, and 3280 for 1 <= x <= 10000. %H A338476 V. Granville, <a href="https://mathoverflow.net/questions/375133/quadratic-progressions-with-very-high-prime-density">Quadratic progressions with very high prime density</a>, MathOverflow. %F A338476 a(n) = 398*A338477(n)^2-1. %e A338476 a(3) = 398*4^2-1 = 6367 is prime. %p A338476 select(isprime, [seq(398*x^2-1,x=1..1000)]); %t A338476 Select[398 Range[100]^2-1,PrimeQ] (* _Harvey P. Dale_, Jan 13 2023 *) %Y A338476 Cf. A331947(11)=398, A338477. %K A338476 nonn %O A338476 1,1 %A A338476 _Robert Israel_, Oct 29 2020