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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 15 |
| 3 | 70 |
| 4 | 630 |
| 5 | 2772 |
| 6 | 48048 |
| 7 | 205920 |
| 8 | 3500640 |
| 9 | 29560960 |
| 10 | 496624128 |
| 11 | 2076791808 |
| 12 | 138452787200 |
| 13 | 575111577600 |
| 14 | 9530420428800 |
| 15 | 157569617756160 |
| 16 | 5199797385953280 |
| 17 | 21410930412748800 |
| 18 | 1408363422705254400 |
[1,3,15,70,630,2772,48048,205920,3500640,29560960, 496624128,2076791808,138452787200,575111577600, 9530420428800,157569617756160,5199797385953280, 21410930412748800,1408363422705254400] |