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%I #41 Feb 11 2020 10:09:54
%S 6,20,315,280,66,3003,78,9520,305235,20900,138,19734,6,7540,15575175,
%T 590240,6,107666559,222,11996600,50536395,19780,282,31534932,66,1060,
%U 48532365,738920,354,83912718435,366,1180480,485415,1340,60918,3667092237666,438,740
%N a(n) = denominator(B°(2*n))/4 where the B°(n) are Zagier's modified Bernoulli numbers.
%C Sequence given for a(1)-a(15) in Note 6.2, p. 13 of Dixit and others.
%H Seiichi Manyama, <a href="/A216912/b216912.txt">Table of n, a(n) for n = 1..500</a>
%H M. W. Coffey, V. de Angelis, A. Dixit, V. H. Moll, et al., <a href="https://arxiv.org/abs/1303.6590">The Zagier polynomials. Part II: Arithmetic properties of coefficients</a>, arXiv:1303.6590 [math.NT], 2013.
%H A. Dixit, V. H. Moll, Ch. Vignat, <a href="http://arxiv.org/abs/1209.4110">The Zagier modification of Bernoulli numbers and a polynomial extension. Part I</a>, arXiv:1209.4110v1 [math.NT], Sep 18, 2012.
%p A216912 := n -> denom(add(binomial(2*n+r,2*r)*bernoulli(r)/(2*n+r),r=0..2*n))/4;
%p seq(A216912(i),i=1..38); # _Peter Luschny_, Sep 20 2012
%t a[n_] := Denominator[Sum[Binomial[2n+r, 2r]*(BernoulliB[r]/(2n+r)), {r, 0, 2n}]]/4;
%t Array[a, 38] (* _Jean-François Alcover_, Jul 14 2018, after _Peter Luschny_ *)
%o (PARI) a(n) = denominator(sum(k=0, 2*n, binomial(2*n+k, 2*k)*bernfrac(k)/(2*n+k)))/4; \\ _Michel Marcus_, Jul 14 2018
%Y Cf. A216922, A216923.
%K nonn
%O 1,1
%A _Jonathan Vos Post_, Sep 20 2012
%E a(16)-a(38) from _Peter Luschny_, Sep 20 2012
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