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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 24 |
| 3 | 104 |
| 4 | 480 |
| 5 | 2112 |
| 6 | 8752 |
| 7 | 34848 |
| 8 | 135168 |
| 9 | 513792 |
| 10 | 1920000 |
| 11 | 7071744 |
| 12 | 25728256 |
| 13 | 92622336 |
| 14 | 330405888 |
| 15 | 1169217536 |
| 16 | 4108296192 |
| 17 | 14344470528 |
| 18 | 49802211328 |
| 19 | 172027060224 |
| 20 | 591476293632 |
| 21 | 2025119416320 |
| 22 | 6907067105280 |
| 23 | 23474916556800 |
| 24 | 79524883136512 |
| 25 | 268595063291904 |
[1,6,24,104,480,2112,8752,34848,135168,513792, 1920000,7071744,25728256,92622336,330405888, 1169217536,4108296192,14344470528,49802211328, 172027060224,591476293632,2025119416320, 6907067105280,23474916556800,79524883136512, 268595063291904] |