D[LerchPhi[z, s, a], {a, n}] == Pochhammer[1 - n - s, n] Sum[z^k/((a + k)^n ((a + k)^2)^(s/2)), {k, 0, Infinity}] /; Abs[z] < 1 && !(Element[-a, Integers] && -a >= 0) && Element[n, Integers] && n >= 0

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2007-05-02