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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 12 |
| 3 | 114 |
| 4 | 1008 |
| 5 | 8676 |
| 6 | 73872 |
| 7 | 626184 |
| 8 | 5298048 |
| 9 | 44791056 |
| 10 | 378551232 |
| 11 | 3198883104 |
| 12 | 27030060288 |
| 13 | 228394230336 |
| 14 | 1929828955392 |
| 15 | 16306120554624 |
| 16 | 137778577993728 |
| 17 | 1164159319286016 |
| 18 | 9836554491620352 |
| 19 | 83113874320863744 |
| 20 | 702269857101754368 |
[1,12,114,1008,8676,73872,626184,5298048,44791056, 378551232,3198883104,27030060288,228394230336, 1929828955392,16306120554624,137778577993728, 1164159319286016,9836554491620352, 83113874320863744,702269857101754368] |