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| n | a(n) |
|---|---|
| 4 | 2 |
| 5 | 30 |
| 6 | 315 |
| 7 | 2856 |
| 8 | 23940 |
| 9 | 191268 |
| 10 | 1480050 |
| 11 | 11196900 |
| 12 | 83304936 |
| 13 | 611931320 |
| 14 | 4450217772 |
| 15 | 32104210320 |
| 16 | 230080173960 |
| 17 | 1639890119016 |
| 18 | 11634355574100 |
| 19 | 82216112723640 |
| 20 | 579022013389050 |
| 21 | 4065827626164150 |
| 22 | 28475852003986695 |
[2,30,315,2856,23940,191268,1480050,11196900, 83304936,611931320,4450217772,32104210320, 230080173960,1639890119016,11634355574100, 82216112723640,579022013389050,4065827626164150, 28475852003986695] |