x

Exact $E_1\left(x\right)$

from ref. [1]

Computed $E_1\left(x\right)$

from Equation (18)

Relative

error (%)

Truncation

order n

0.25

1.044282634

1.060604077

1.56293

10

0.50

0.559773595

0.560924075

0.20553

12

0.75

0.340340813

0.340530021

0.05559

14

1.00

0.219383934

0.219420901

0.01685

16

1.25

0.146413373

0.146420344

0.00476

17

1.50

0.100019582

0.100020886

0.00130

19

1.75

0.069488685

0.069488107

0.00083

20

2.00

0.048900511

0.048900683

0.00035

21

2.50

0.024914917

0.024914947

0.00012

22

3.00

0.013048380

0.013048383

0.00002

24

3.50

0.006970139

0.06970140

0.00000

26

4.00

0.003779352

0.003779352

0.00000

27

4.50

0.002073400

0.002073401

0.00000

27

5.00

0.001148295

0.001148296

0.00000

27