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 A377248 #23 Nov 22 2024 10:09:08 %S A377248 12,20,412,712,2092,4704,10176,33396,41124,105604,139780,142924 %N A377248 Numbers k such that 8191 * 2^k + 1 is prime. %C A377248 8191 is the 5th Mersenne prime: 8191 = 2^13 - 1 (a term of A000668). %e A377248 12 is a term, because 8191 * 2^12 + 1 = 8191 * 4096 + 1 = 33550337 is prime. (also a term of A061644). %o A377248 (PARI) is(k) = isprime(8191 * 2^k + 1); %Y A377248 Cf. A000668, A002253, A002254, A001771, A061644. %K A377248 nonn,more %O A377248 1,1 %A A377248 _Arsen Vardanyan_, Oct 21 2024 %E A377248 a(8)-a(9) from _Hugo Pfoertner_, Oct 21 2024 %E A377248 a(10)-a(12) from _Michael S. Branicky_, Nov 05 2024