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%I #8 Jun 25 2020 02:57:11
%S 1,1,3,1,15,1,7,1,15,1,33,1,455,1,3,1,255,1,133,1,33,1,69,1,455,1,3,1,
%T 435,1,2387,1,255,1,3,1,319865,1,3,1,1353,1,43,1,345,1,141,1,7735
%N a(n) = Denominator(-4*n^2*Zeta(1 - n)^2*(1 - 2^n)) for n >= 1, a(0) = 1.
%F a(n) = denominator(Bernoulli(n)^2*(2^(n+2) - 4)).
%e Rational sequence starts: 0, 1, 1/3, 0, 1/15, 0, 1/7, 0, 17/15, 0, 775/33, 0, 477481/455, ...
%p a := s -> `if`(s = 0, 0, -4*s^2*Zeta(1 - s)^2*(1 - 2^s)):
%p seq(denom(a(s)), s = 0..24);
%Y Cf. A335264 (numerators), A164555/A027642 (Bernoulli numbers).
%Y Cf. A335538, A335539, A327497.
%K nonn,frac
%O 0,3
%A _Peter Luschny_, Jun 13 2020