SeriesCoefficient
SeriesCoefficient[series, n] finds the coefficient of the order term in a power series. SeriesCoefficient[series, , , ... ] finds a coefficient in a multivariate series.
See The Mathematica Book: Section 3.6.5. See also: Coefficient, Normal.
Further Examples
SeriesCoefficient[series, n] finds the coefficient of the 
order term in a power series. 
, 
, ... 
] finds a coefficient in a multivariate series. 
