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A181993
Denominator of (4^n*(4^n-1)/2)*B_{2n}/(2n)!, B_{n} Bernoulli number.
1
1, 2, 6, 15, 630, 2835, 155925, 6081075, 1277025750, 10854718875, 1856156927625, 194896477400625, 2900518163668125, 3698160658676859375, 1298054391195577640625, 263505041412702261046875, 245059688513813102773593750, 4043484860477916195764296875
OFFSET
0,2
COMMENTS
Numerator is (-1)^(n+1)*A046990(n).
FORMULA
a(n) = denominator of (1/Pi)*Integral(x>=0, (sin(x)/x)^(2*n)*sin(2*n*x)*tan(x)).
MAPLE
A181993 := n -> denom((4^n*(4^n-1)/2)*bernoulli(2*n)/(2*n)!);
seq(A181993(i), i=0..18);
MATHEMATICA
a[n_] := Denominator[4^n (4^n-1)/2 BernoulliB[2n]/(2n)!];
Table[a[n], {n, 0, 17}] (* Jean-François Alcover, Jun 18 2019 *)
PROG
(PARI) a(n) = denominator((4^n*(4^n-1)/2)*bernfrac(2*n)/(2*n)!); \\ Michel Marcus, Jun 18 2019
CROSSREFS
Cf. A046990.
Sequence in context: A376051 A261726 A302775 * A123475 A193341 A009711
KEYWORD
nonn,frac
AUTHOR
Peter Luschny, Apr 05 2012
STATUS
approved