D[Erfi[z], {z, n}] == Erfi[z] KroneckerDelta[n] + Boole[n != 0, ((n - 1)!/(2^n Sqrt[Pi])) E^z^2 Sum[(2^(2 k) z^(2 k - n - 1))/((2 k - n - 1)! (n - k)!), {k, 1, n}]] /; Element[n, Integers] && n >= 0

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2001-10-29