Function sph_jy_impl_n 

pub fn sph_jy_impl_n<P, E, V, const N: usize>(x: V) -> (V, V, V, V)
where
    E: FloatElement,
    V: FloatVector<Element = E> + TranscendentalMathWithPolicy,
    P: Policy,

$(j_{n-1},\; j_n,\; y_{n-1},\; y_n)$, on the whole real line.

The neighbour below comes back too, because every derivative identity in this family reaches down one order and the walk passes through it regardless: $f_n' = f_{n-1} - \frac{n+1}{x} f_n$.