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 A229856 #16 Jul 12 2025 21:08:12
%S A229856 257,641,1409,3329,4481,7937,9473,9857,11393,11777,12161,13313,13697,
%T A229856 14081,15233,16001,17921,19073,19457,19841,21377,23297,25601,28289,
%U A229856 30593,30977,35201,35969,36353,37889,38273,39041,40193,40577,40961,41729,43649,44417
%N A229856 Primes of the form 384*k + 257.
%C A229856 Every Fermat number greater than 257 has a prime factor of the form 384*k + 257, k > 0.
%H A229856 Wikipedia, <a href="http://en.wikipedia.org/wiki/Fermat_number">Fermat number</a>
%t A229856 Select[Table[384*n + 257, {n, 0, 115}], PrimeQ]
%o A229856 (Magma) [384*n+257 : n in [0..115] | IsPrime(384*n+257)];
%Y A229856 Subsequence of A107181 (primes of the form 8x^2+9y^2).
%Y A229856 Cf. A000215, A023394, A094358, A229853, A229855, A229856.
%K A229856 nonn
%O A229856 1,1
%A A229856 _Arkadiusz Wesolowski_, Oct 01 2013