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 A219549 #9 Oct 10 2019 04:02:06
%S A219549 257,65537,97,641,257,193,257,274177,97,65537,257,641,257,449,97,
%T A219549 59649589127497217,257,193,257,641,97,65537,257,769,257,65537,97,641,
%U A219549 257,193,257,1238926361552897,97,5441,257,641,257,65537,97,274177,257,193,257,641,97,65537,257,59649589127497217,257,65537,97,641,257,193,257,274177,97,65537,257,641,257,5953
%N A219549 Smallest prime factor of 2^(8n) + 1.
%C A219549 The smallest prime factor of 2^(8n+k) + 1 does not depend on n if 0 < k < 8 (see Formula in A002586).
%C A219549 For references and links, see A002586.
%H A219549 Chai Wah Wu, <a href="/A219549/b219549.txt">Table of n, a(n) for n = 1..223</a>
%F A219549 a(n) = A002586(8n) = A020639(2^(8n) + 1).
%F A219549 a(2^(k-3)) = A020639(A000215(k)) is the smallest prime factor of the k-th Fermat number 2^(2^k) + 1.
%e A219549 a(1) = 2^8 + 1 = 257 is the Fermat prime A019434(3).
%e A219549 a(2) = 2^16 + 1 = 65537 is the Fermat prime A019434(4).
%t A219549 Table[FactorInteger[2^(8*n) + 1][[1, 1]], {n, 20}] (* _T. D. Noe_, Nov 29 2012 *)
%Y A219549 Cf. A000215, A002586, A019434, A020639.
%K A219549 nonn
%O A219549 1,1
%A A219549 _Jonathan Sondow_, Nov 28 2012