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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 5 |
| 3 | 20 |
| 4 | 121 |
| 5 | 982 |
| 6 | 9933 |
| 7 | 120168 |
| 8 | 1692273 |
| 9 | 27196522 |
| 10 | 491229653 |
| 11 | 9851789564 |
| 12 | 217230600041 |
| 13 | 5223386190526 |
| 14 | 136025271553693 |
| 15 | 3813930989693904 |
| 16 | 114553954962370785 |
| 17 | 3669540489785558994 |
| 18 | 124878930607671376549 |
| 19 | 4499311042365955114724 |
| 20 | 171098698540513965736025 |
[1,2,5,20,121,982,9933,120168,1692273,27196522, 491229653,9851789564,217230600041,5223386190526, 136025271553693,3813930989693904, 114553954962370785,3669540489785558994, 124878930607671376549,4499311042365955114724, 171098698540513965736025] |