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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 10 |
| 3 | 90 |
| 4 | 1224 |
| 5 | 22450 |
| 6 | 517920 |
| 7 | 14395514 |
| 8 | 468414464 |
| 9 | 17474840226 |
| 10 | 735559614720 |
| 11 | 34491849224602 |
| 12 | 1783268816102400 |
| 13 | 100786369113730898 |
| 14 | 6182264844496971776 |
| 15 | 409065938149354422330 |
| 16 | 29043282491002728284160 |
| 17 | 2202461172795524123296834 |
| 18 | 177675452451923238962528256 |
[1,2,10,90,1224,22450,517920,14395514,468414464, 17474840226,735559614720,34491849224602, 1783268816102400,100786369113730898, 6182264844496971776,409065938149354422330, 29043282491002728284160,2202461172795524123296834, 177675452451923238962528256] |