where `` an '' represents the coefficient of the `` n `` th term , `` c '' is a constant , and `` x '' varies around `` c '' ( for this reason one sometimes speaks of the series as being `` centered '' at `` c '' ) .
where `` an '' represents the coefficient of the nth term , `` c '' is a constant , and `` x '' varies around `` c '' ( for this reason one sometimes speaks of the series as being `` centered '' at `` c '' ) .