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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 7 |
| 3 | 41 |
| 4 | 314 |
| 5 | 2194 |
| 6 | 22764 |
| 7 | 195348 |
| 8 | 2374224 |
| 9 | 27940176 |
| 10 | 384636960 |
| 11 | 4673720160 |
| 12 | 95522440320 |
| 13 | 1323221996160 |
| 14 | 23481816503040 |
| 15 | 489968947641600 |
| 16 | 10853692580505600 |
| 17 | 190580382936115200 |
| 18 | 5408424680491929600 |
| 19 | 105077728210820198400 |
| 20 | 3399507785578641408000 |
[1,7,41,314,2194,22764,195348,2374224,27940176, 384636960,4673720160,95522440320,1323221996160, 23481816503040,489968947641600,10853692580505600, 190580382936115200,5408424680491929600, 105077728210820198400,3399507785578641408000] |