Table 1: (a) Harmonic term convergence for various amplitudes (1st resonant frequency). (b) Harmonic term convergence for various amplitudes (2nd resonant frequency).
(a)

Homotopy perturbationNo. of harmonic terms = 123

0.643480.643470.64347
0.60.661400.661400.660940.66091
10.677590.677590.676410.67619
1.40.687210.687210.685800.68530

(b)

Homotopy perturbationNo. of harmonic terms = 123

1.077861.077841.07784
0.61.195391.195391.19361.19356
11.406611.406611.40051.40024
1.41.667151.667151.652191.6600