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 A204322 #27 Jan 04 2024 15:45:25 %S A204322 0,2,6,18,50,290,2582,20462,23870,26342,31938,38122,65034,70130, %T A204322 245538,851878,1052422,1496566,5380542,8431178 %N A204322 Numbers k such that 4*5^k + 1 is prime. %C A204322 All terms correspond to verified primes, that is, not merely probable primes. - _Robert Price_, Jan 16 2015 %C A204322 a(16) > 3*10^5. - _Robert Price_, Jan 16 2015 %t A204322 Select[Range[0,2000], PrimeQ[4*5^#+1]&] %o A204322 (PARI) is(n)=ispseudoprime(4*5^n+1) \\ _Charles R Greathouse IV_, Jun 13 2017 %K A204322 nonn,more %O A204322 1,2 %A A204322 _José María Grau Ribas_, Jan 14 2012 %E A204322 a(8)-a(15) from _Robert Price_, Jan 16 2015 %E A204322 a(16)-a(19) from _Ryan Propper_, Dec 20 2023 %E A204322 a(20) from _Ryan Propper_, Jan 04 2024