equation icon  ( ) 1 s2 [(l + 1)2- s2]2 (l2 - s2)2 2 3 n = l + ------ -2 - --------+ ------------------------- ------------------ e + O(e ).(173) 2l + 1 l(l + 1) (2l + 1)(2l + 2)(2l + 3) (2l - 1)2l(2l + 1)