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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 14 |
| 4 | 66 |
| 5 | 444 |
| 6 | 2880 |
| 7 | 25080 |
| 8 | 216720 |
| 9 | 2247840 |
| 10 | 24071040 |
| 11 | 304335360 |
| 12 | 3752179200 |
| 13 | 54965433600 |
| 14 | 810550540800 |
| 15 | 13176376012800 |
| 16 | 219079045785600 |
| 17 | 4078723532083200 |
| 18 | 75227891042304000 |
| 19 | 1550619342784512000 |
| 20 | 31871016307113984000 |
| 21 | 710529031487987712000 |
| 22 | 16180987966182014976000 |
[1,3,14,66,444,2880,25080,216720,2247840,24071040, 304335360,3752179200,54965433600,810550540800, 13176376012800,219079045785600,4078723532083200, 75227891042304000,1550619342784512000, 31871016307113984000,710529031487987712000, 16180987966182014976000] |