p0 is the overall normalization.  p1 is the cos term for N=1, p2 is the sin term for N=1.  p3 is the cos term for N=2, etc.  Results below.

p0              = 0.   !69.8261          +/- 3.665        (5.248%)
p1              = 21.3148          +/- 5.117        (24.01%)
p2              = -26.0336         +/- 5.252        (20.17%)
p3              = 32.1604          +/- 5.125        (15.94%)
p4              = 25.3056          +/- 5.242        (20.71%)
p5              = 11.349           +/- 5.097        (44.91%)
p6              = 4.89845          +/- 5.262        (107.4%)
p7              = 33.8466          +/- 5.282        (15.61%)
p8              = 12.2211          +/- 5.097        (41.71%)
p9              = -5.04669         +/- 5.263        (104.3%)
p10             = 3.83287          +/- 5.11         (133.3%)
p11             = 37.4812          +/- 5.303        (14.15%)
p12             = 3.34991          +/- 5.07         (151.3%)
p13             = 10.4991          +/- 5.214        (49.66%)
p14             = -11.587          +/- 5.196        (44.85%)
p15             = 9.96784          +/- 5.23         (52.47%)
p16             = 6.67647          +/- 5.157        (77.24%)
p17             = 0.845698         +/- 5.23         (618.5%)
p18             = -2.35758         +/- 5.158        (218.8%)
p19             = 4.12316          +/- 5.055        (122.6%)
p20             = 10.966           +/- 5.361        (48.89%)