A335265 a(n) = Denominator(-4*n^2*Zeta(1 - n)^2*(1 - 2^n)) for n >= 1, a(0) = 1.

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, 435, 1, 2387, 1, 255, 1, 3, 1, 319865, 1, 3, 1, 1353, 1, 43, 1, 345, 1, 141, 1, 7735

Offset: 0

Author

Peter Luschny, Jun 13 2020

Keywords

• nonn
• frac

Examples

			Rational sequence starts: 0, 1, 1/3, 0, 1/15, 0, 1/7, 0, 17/15, 0, 775/33, 0, 477481/455, ...
		

Crossrefs

Cf. A335264 (numerators), A164555/A027642 (Bernoulli numbers).

Cf. A335538, A335539, A327497.

Programs

Maple

a := s -> `if`(s = 0, 0, -4*s^2*Zeta(1 - s)^2*(1 - 2^s)):
seq(denom(a(s)), s = 0..24);

Formula

a(n) = denominator(Bernoulli(n)^2*(2^(n+2) - 4)).