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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 10 |
| 4 | 60 |
| 5 | 358 |
| 6 | 2798 |
| 7 | 22249 |
| 8 | 186765 |
| 9 | 1596162 |
| 10 | 13907330 |
| 11 | 122758794 |
| 12 | 1096122478 |
| 13 | 9880366438 |
| 14 | 89796245827 |
| 15 | 821927851286 |
| 16 | 7570508171686 |
| 17 | 70115797179348 |
| 18 | 652594351781036 |
| 19 | 6100765243003922 |
| 20 | 57259681174637899 |
| 21 | 539353919732122101 |
| 22 | 5097036850039818860 |
[1,4,10,60,358,2798,22249,186765,1596162,13907330, 122758794,1096122478,9880366438,89796245827, 821927851286,7570508171686,70115797179348, 652594351781036,6100765243003922, 57259681174637899,539353919732122101, 5097036850039818860] |