Function polynomial_sw1d 

fn polynomial_sw1d<const N: usize>(
    l: i32,
    m: i32,
    n: i32,
    rho2: Jet<N>,
    beta: Jet<N>,
    azimuth: Jet<N>,
) -> Jet<N>

The inner sum S_lmn of the 1D spherical summand of reciprocal_term (upstream _s_sum_sw1d times (-1)^m e^(i m phi)), with rho2 = (k rho)^2, beta = q_z / k and the azimuth phi of the shift: sum_s (k rho)^(2n - s) beta^(l - s) (-1)^m e^(i m phi) / ((n - (s + |m|) / 2)! (n - (s - |m|) / 2)! (l - s)! (s - n)!) over s = n..=min(2n - |m|, l) with even s - |m|.