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A281662 (Denominator of Bernoulli(2*n)) read mod n.

%I A281662 #16 Jan 30 2017 05:44:27
%S A281662 0,0,0,2,1,0,6,6,6,0,6,6,6,2,12,14,6,12,6,10,0,8,6,18,16,4,15,2,6,0,6,
%T A281662 30,9,30,31,30,6,30,3,10,6,0,6,30,3,30,6,42,6,30,42,30,6,30,33,6,42,
%U A281662 30,6,30,6,30,42,62,1,24,6,30,42,50,6,6,6,30,72,30,61
%N A281662 (Denominator of Bernoulli(2*n)) read mod n.
%C A281662 Odd terms at: 5, 27, 33, 35, 39, 45, 55, 65, 77, 81, 99, 105, 121, etc. - _Robert G. Wilson v_, Jan 26 2017
%H A281662 Seiichi Manyama, <a href="/A281662/b281662.txt">Table of n, a(n) for n = 1..1000</a>
%F A281662 a(n) = A002445(n) mod n.
%t A281662 f[n_] := Mod[Denominator[BernoulliB[2 n]], n]; Array[f, 77] (* _Robert G. Wilson v_, Jan 26 2017 *)
%o A281662 (Ruby)
%o A281662 def bernoulli(n)
%o A281662   ary = []
%o A281662   a = []
%o A281662   (0..n).each{|i|
%o A281662     a << 1r / (i + 1)
%o A281662     i.downto(1){|j| a[j - 1] = j * (a[j - 1] - a[j])}
%o A281662     ary << a[0]
%o A281662   }
%o A281662   ary
%o A281662 end
%o A281662 def A281662(n)
%o A281662   a = bernoulli(2 * n)
%o A281662   (1..n).map{|i| a[2 * i].denominator % i}
%o A281662 end
%o A281662 (PARI) a(n) = denominator(bernfrac(2*n)) % n; \\ _Michel Marcus_, Jan 29 2017
%Y A281662 Cf. A002445, A106741, A281648.
%K A281662 nonn
%O A281662 1,4
%A A281662 _Seiichi Manyama_, Jan 26 2017