Confuse to collect the coefficient

*To*: mathgroup at smc.vnet.net*Subject*: [mg114413] Confuse to collect the coefficient*From*: Autt <utt_alert90 at hotmail.com>*Date*: Fri, 3 Dec 2010 05:23:24 -0500 (EST)

I have to collect the coefficient of Taylor series but It doesn't work eg. n = 3 u = Normal[Series[x^2 + y^2, {x, 5, n}, {y, 5, n}]] d = {}; q[0] = {}; For[k = 1 , k <= n - 1, k++, For[i = 0 , i <= k , i++, p[i, k - i] = SeriesCoefficient[u, {x, 5, i}, {y, 5, k - i}]; q[k] = Union[{q[k - 1], {p[i, k - i]}}]; d = Union[d, q[k]]; Print[p[i, k - i]];]] Print[q[1]]; Print[d]; In the finally the results of d is {{},{0},{1},{10},{{},{10}}} Why is cannot union all of this in to the form of {0,1,10}