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 A219548 #8 Nov 27 2012 12:05:01 %S A219548 257,65537,641,257,193,257,274177,65537,257,641,257,449, %T A219548 59649589127497217,257,257,641,65537,257,769,257,65537,641,257,193, %U A219548 257,1238926361552897,5441,257,257,65537,274177,257,193,257,641,65537,257,59649589127497217,257,65537,641,257,257,274177,65537,257,641,257,5953 %N A219548 Smallest prime factor of 2^A219547(n) + 1. %C A219548 2p divides sigma_k(2p), where p = a(n) and k = A219547(n). But 2p is not the least m > 1 that divides sigma_k(m). %F A219548 a(n) = A002586(A219547(n)). %Y A219548 Cf. A002586, A219547. %K A219548 nonn %O A219548 1,1 %A A219548 _Jonathan Sondow_, Nov 24 2012