A249909 - OEIS

%I #64 Dec 18 2014 02:10:52

%S 1,1,1,1,1,1,1,61,1,277,1,19,691,43,1,47,3617,228135437,43867,79,283,

%T 41737,131,31,103,2137,657931,67,9349,71,1721,15669721,37,930157,

%U 151628697551,4153,26315271553053477373,9257,154210205991661,23489580527043108252017828576198947741,137616929,763601

%N Smallest prime factor of A241601(n), or 1 if A241601(n) = 1.

%C Also the smallest prime factor of A246006(n) that is >= n+2.

%C a(n) = A020639(A241601(n)).

%C a(n) = 1 iff n is in the set {0, 1, 2, 3, 4, 5, 6, 8, 10, 14}.

%C a(189) is currently unknown; a(190)..a(199) = {5101, 559570609330768709, 40833790860803270336710504624737304862569304959957, 311, 467, 34110029, 461, 26034939865747697437451558982836040663625026070193, 34470847, 1879}.

%C All terms are Bernoulli or Euler irregular primes.

%H Eric Chen, <a href="/A249909/b249909.txt">Table of n, a(n) for n = 0..188</a>

%H Samuel Wagstaff, <a href="http://homes.cerias.purdue.edu/~ssw/bernoulli/index.html">Factorization of Bernoulli and Euler numbers</a>

%t a246006[n_] := If[EvenQ[n], Abs[Numerator[BernoulliB[n]]], Abs[EulerE[n-1]]];

%t a241601[n_] := a246006[n]/GCD[a246006[n], n!]

%t a = {}; Do[a = Append[a, FactorInteger[a241601[n]][[1, 1]]], {n, 0, 99} ]; a

%K nonn

%O 0,8

%A _Eric Chen_, Dec 15 2014