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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 32 |
| 5 | 300 |
| 6 | 864 |
| 7 | 17612 |
| 8 | 74752 |
| 9 | 1152792 |
| 10 | 6470400 |
| 11 | 220057992 |
| 12 | 719622144 |
| 13 | 40754156352 |
| 14 | 192835098624 |
| 15 | 4787867880000 |
| 16 | 55181218873344 |
| 17 | 3071730630989952 |
| 18 | 11004144881762304 |
| 19 | 1179255538492239744 |
| 20 | 5720352215040000000 |
| 21 | 253837962769406045184 |
| 22 | 3262870639485701849088 |
[1,1,2,9,32,300,864,17612,74752,1152792,6470400, 220057992,719622144,40754156352,192835098624, 4787867880000,55181218873344,3071730630989952, 11004144881762304,1179255538492239744, 5720352215040000000,253837962769406045184, 3262870639485701849088] |