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EI.KEY
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1993-11-14
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355b
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* ei external
ei(x) is the exponential integral function Ei(x),
ei(x) = inte(e^t/t, t,-inf,x), ei'(x) = e^x/x.
ei(n,x) is the incomplete exponential integral function,
ei(n,x) = inte(t^n*e^t, t,-inf,x), d(ei(n,x),x) = x^n*e^x, ei(-1, x) =
ei(x), ei(0,x) = e^x.
See also: gamma, erf, ci, si, li.