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 A249909 #64 Dec 18 2014 02:10:52
%S A249909 1,1,1,1,1,1,1,61,1,277,1,19,691,43,1,47,3617,228135437,43867,79,283,
%T A249909 41737,131,31,103,2137,657931,67,9349,71,1721,15669721,37,930157,
%U A249909 151628697551,4153,26315271553053477373,9257,154210205991661,23489580527043108252017828576198947741,137616929,763601
%N A249909 Smallest prime factor of A241601(n), or 1 if A241601(n) = 1.
%C A249909 Also the smallest prime factor of A246006(n) that is >= n+2.
%C A249909 a(n) = A020639(A241601(n)).
%C A249909 a(n) = 1 iff n is in the set {0, 1, 2, 3, 4, 5, 6, 8, 10, 14}.
%C A249909 a(189) is currently unknown; a(190)..a(199) = {5101, 559570609330768709, 40833790860803270336710504624737304862569304959957, 311, 467, 34110029, 461, 26034939865747697437451558982836040663625026070193, 34470847, 1879}.
%C A249909 All terms are Bernoulli or Euler irregular primes.
%H A249909 Eric Chen, <a href="/A249909/b249909.txt">Table of n, a(n) for n = 0..188</a>
%H A249909 Samuel Wagstaff, <a href="http://homes.cerias.purdue.edu/~ssw/bernoulli/index.html">Factorization of Bernoulli and Euler numbers</a>
%t A249909 a246006[n_] := If[EvenQ[n], Abs[Numerator[BernoulliB[n]]], Abs[EulerE[n-1]]];
%t A249909 a241601[n_] := a246006[n]/GCD[a246006[n], n!]
%t A249909 a = {}; Do[a = Append[a, FactorInteger[a241601[n]][[1, 1]]], {n, 0, 99} ]; a
%K A249909 nonn
%O A249909 0,8
%A A249909 _Eric Chen_, Dec 15 2014