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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 12 |
| 3 | 104 |
| 4 | 1216 |
| 5 | 18112 |
| 6 | 329600 |
| 7 | 7108096 |
| 8 | 177549312 |
| 9 | 5046554624 |
| 10 | 160947232768 |
| 11 | 5694342479872 |
| 12 | 221410157133824 |
| 13 | 9387011838312448 |
| 14 | 431051678297358336 |
| 15 | 21316106766591721472 |
| 16 | 1129526392342026649600 |
| 17 | 63855305138514241257472 |
| 18 | 3836490516381680506241024 |
[1,2,12,104,1216,18112,329600,7108096,177549312, 5046554624,160947232768,5694342479872, 221410157133824,9387011838312448, 431051678297358336,21316106766591721472, 1129526392342026649600,63855305138514241257472, 3836490516381680506241024] |