“…This test example (1), (2), (59) was considered in [16,17,18,19,20] in which the following methods were applied: Adomian decomposition method (ADM) [16], variational iteration method (VIM) [17], homotopy perturbation method (HPM) [18] homotopy analysis method (HAM) [19], extended sampling method (ESM) [20]. Let us compare the behavior of the absolute errors [16,17,18,19,20] as the index number n of eigenvalue increases.…”