This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A335265 #8 Jun 25 2020 02:57:11 %S A335265 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 A335265 435,1,2387,1,255,1,3,1,319865,1,3,1,1353,1,43,1,345,1,141,1,7735 %N A335265 a(n) = Denominator(-4*n^2*Zeta(1 - n)^2*(1 - 2^n)) for n >= 1, a(0) = 1. %F A335265 a(n) = denominator(Bernoulli(n)^2*(2^(n+2) - 4)). %e A335265 Rational sequence starts: 0, 1, 1/3, 0, 1/15, 0, 1/7, 0, 17/15, 0, 775/33, 0, 477481/455, ... %p A335265 a := s -> `if`(s = 0, 0, -4*s^2*Zeta(1 - s)^2*(1 - 2^s)): %p A335265 seq(denom(a(s)), s = 0..24); %Y A335265 Cf. A335264 (numerators), A164555/A027642 (Bernoulli numbers). %Y A335265 Cf. A335538, A335539, A327497. %K A335265 nonn,frac %O A335265 0,3 %A A335265 _Peter Luschny_, Jun 13 2020