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advanced sum problem ? - tommy1729 - 09/11/2010
what is the radius of convergence for sum ( r over all rationals >= 0 ) a_r z^r for real a_r coefficients and when expanded at z = a ? a_r is analytic. in fact how to change the expanding point ? so lets start the question for z= a = 0. i assume for bounded a_r integral a_r dr must have oo zero's on the real line is a necc condition. maybe for bounded a_r and integral a_r z^r dr converges and has oo zero's on the real line for real z determines the radius >= z ( expanded at 0 ). |