N

Midpoint error

rate

Richardson’s extrap.

rate

8

0.007024577280901

−0.00011693442490234

16

0.0017507392430902

4.01234

−7.20676951360e−06

16.22563

32

0.0004373481675656

4.00307

−4.4885760908108e−07

16.05580

64

0.00010931601997121

4.00076

−2.80292269394e−08

16.01391

128

2.7327691408896e-05

4.00019

−1.7514452110845e−09

16.00348