GNU Scientific Library Reference Manual - Third Edition (v1.12) by M. Galassi, J. Davies, J. Theiler, B. Gough, G. Jungman, P. Alken, M. Booth, F. Rossi Paperback (6"x9"), 592 pages, 60 figures ISBN 0954612078 RRP £24.95 ($39.95) Get a printed copy>>>

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7.17.1 Exponential Integral

Function: double gsl_sf_expint_E1 (double x)

Function: int gsl_sf_expint_E1_e (double x, gsl_sf_result * result)

These routines compute the exponential integral E_1(x),

E_1(x) := \Re \int_1^\infty dt \exp(-xt)/t.

Function: double gsl_sf_expint_E2 (double x)

Function: int gsl_sf_expint_E2_e (double x, gsl_sf_result * result)

These routines compute the second-order exponential integral E_2(x),

E_2(x) := \Re \int_1^\infty dt \exp(-xt)/t^2.

Function: double gsl_sf_expint_En (int n, double x)

Function: int gsl_sf_expint_En_e (int n, double x, gsl_sf_result * result)

These routines compute the exponential integral E_n(x) of order n,

E_n(x) := \Re \int_1^\infty dt \exp(-xt)/t^n.