Function zeta_int 

pub fn zeta_int<E: FloatElement + PolylogConsts + BernoulliNumbers>(
    n: isize,
) -> E

zeta(n) at an integer: the table for n >= 2 (exactly 1 past it), -1/2 at zero, -B_{j+1}/(j+1) at -j (zero for even j).

Past the Bernoulli table it returns zero, not infinity: the table ends where B_{2n} overflows the format, and every use here divides by a k! that overflowed earlier still, so the true coefficient is far below the format’s precision and the honest value of inf/inf is 0, not NaN. Reached in binary32 from k = 58.