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 A358621 #6 Nov 27 2022 11:06:32 %S A358621 2,2,160,140,2800,8660,62150,4085530,922820,4629490,5802710, %T A358621 1146175000,90894850 %N A358621 Smallest b > 1 such that b^(2^n)+1 is a Sophie Germain prime. %C A358621 In other words, 2*b^(2^n)+3 is also prime. %C A358621 For n > 1, a(n) ends in 0 because b is even (or else b^(2^n)+1 would have 2 as a proper divisor) and b == 0 (mod 5) (or else 2*b^(2^n)+3 would have 5 as a proper divisor). %H A358621 PrimeGrid and "Stream", <a href="https://www.primegrid.com/forum_thread.php?id=9538">GFN-1x Small Primes search</a>, mentions a(12). %o A358621 (PARI) a(n)=n<2&&return(2);forstep(b=10,+oo,10,ispseudoprime(b^(2^n)+1)&&ispseudoprime(2*b^(2^n)+3)&&return(b)) %Y A358621 Cf. A005384, A056993, A182154. %K A358621 nonn,hard,more %O A358621 0,1 %A A358621 _Jeppe Stig Nielsen_, Nov 23 2022