%I #9 Jun 25 2020 02:57:03
%S 1,1,9,1,1350,1,52920,1,1134000,1,11290752,1,74373979680000,1,
%T 8006169600,1,12147360825600000,1,56625794240311296000,1,
%U 3311787858630451200000,1,451287524451778560000,1,48168123888308960600064000000,1,10738530029998374912000000,1
%N a(n) = Denominator(-4*n^2*Zeta(1 - n)*Zeta(n)*(1 - 2^(1 - n)) / Pi^n) for n >= 2, a(0) = 0, a(1) = 1.
%F a(n) = denominator(n*Bernoulli(n)*Zeta(n)*(4-2^(3-n))/Pi^n)) for n >= 2.
%e Rational sequence starts: 0, 1, 1/9, 0, -7/1350, 0, 31/52920, 0, -127/1134000, 0, 365/11290752, ...
%p a := s -> `if`(s = 1 or s = 0, s, -4*s^2*Zeta(1 - s)*Zeta(s)*(1 - 2^(1 - s))/Pi^s):
%p seq(denom(a(s)), s = 0..34);
%Y Cf. A335538 (numerators), A164555/A027642 (Bernoulli numbers).
%Y Cf. A335264, A335265, A327497.
%K nonn,frac
%O 0,3
%A _Peter Luschny_, Jun 13 2020