(n, Z=1)
return -Z**2/(2*n**2)
Returns the energy of the state (n, l) in Hartree atomic units.

    The energy doesn't depend on "l".

    Examples
    ========

    >>> from sympy import var
    >>> from sympy.physics.hydrogen import E_nl
    >>> var("n Z")
    (n, Z)
    >>> E_nl(n, Z)
    -Z**2/(2*n**2)
    >>> E_nl(1)
    -1/2
    >>> E_nl(2)
    -1/8
    >>> E_nl(3)
    -1/18
    >>> E_nl(3, 47)
    -2209/18
Returns the energy of the state (n, l) in Hartree atomic units.
Returns the energy of the state ( n l ) in Hartree atomic units .
def E_nl(n, Z=1):
    """
    Returns the energy of the state (n, l) in Hartree atomic units.

    The energy doesn't depend on "l".

    Examples
    ========

    >>> from sympy import var
    >>> from sympy.physics.hydrogen import E_nl
    >>> var("n Z")
    (n, Z)
    >>> E_nl(n, Z)
    -Z**2/(2*n**2)
    >>> E_nl(1)
    -1/2
    >>> E_nl(2)
    -1/8
    >>> E_nl(3)
    -1/18
    >>> E_nl(3, 47)
    -2209/18

    """
    n, Z = S(n), S(Z)
    if n.is_integer and (n < 1):
        raise ValueError("'n' must be positive integer")
    return -Z**2/(2*n**2)
def E_nl ( n , Z = 1 ) : n , Z = S ( n ) , S ( Z ) if n . is_integer and ( n < 1 ) : raise ValueError ( "'n' must be positive integer" ) return - Z ** 2 / ( 2 * n ** 2 )