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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 552 |
| 7 | 2826 |
| 8 | 17080 |
| 9 | 117816 |
| 10 | 943250 |
| 11 | 7369128 |
| 12 | 63533572 |
| 13 | 603300392 |
| 14 | 6280101222 |
| 15 | 71927971040 |
| 16 | 836503868762 |
[1,2,6,24,120,552,2826,17080,117816,943250, 7369128,63533572,603300392,6280101222,71927971040, 836503868762] |