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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 3 |
| 4 | 104 |
| 5 | 630 |
| 6 | 19944 |
| 7 | 259560 |
| 8 | 8718464 |
| 9 | 185086944 |
| 10 | 6914815200 |
| 11 | 206059083120 |
| 12 | 8700740615808 |
| 13 | 332779651158240 |
| 14 | 15916427365716864 |
| 15 | 738672634596405600 |
| 16 | 39847940942657495040 |
| 17 | 2163098542598925281280 |
| 18 | 130682368989193123952640 |
[1,0,2,3,104,630,19944,259560,8718464,185086944, 6914815200,206059083120,8700740615808, 332779651158240,15916427365716864, 738672634596405600,39847940942657495040, 2163098542598925281280,130682368989193123952640] |