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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 28 |
| 5 | 160 |
| 6 | 1086 |
| 7 | 8624 |
| 8 | 78296 |
| 9 | 799488 |
| 10 | 9070810 |
| 11 | 113208832 |
| 12 | 1541351604 |
| 13 | 22734473216 |
| 14 | 361121134934 |
| 15 | 6145880954880 |
| 16 | 111569141960752 |
| 17 | 2151953994809344 |
| 18 | 43948641637067058 |
| 19 | 947412315736506368 |
[0,1,2,6,28,160,1086,8624,78296,799488,9070810, 113208832,1541351604,22734473216,361121134934, 6145880954880,111569141960752,2151953994809344, 43948641637067058,947412315736506368] |