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| n | a(n) |
|---|---|
| 4 | 1 |
| 5 | 10 |
| 6 | 60 |
| 7 | 280 |
| 8 | 1120 |
| 9 | 4032 |
| 10 | 13440 |
| 11 | 42240 |
| 12 | 126720 |
| 13 | 366080 |
| 14 | 1025024 |
| 15 | 2795520 |
| 16 | 7454720 |
| 17 | 19496960 |
| 18 | 50135040 |
| 19 | 127008768 |
| 20 | 317521920 |
| 21 | 784465920 |
| 22 | 1917583360 |
| 23 | 4642570240 |
| 24 | 11142168576 |
| 25 | 26528972800 |
| 26 | 62704844800 |
| 27 | 147220070400 |
[1,10,60,280,1120,4032,13440,42240,126720,366080, 1025024,2795520,7454720,19496960,50135040, 127008768,317521920,784465920,1917583360, 4642570240,11142168576,26528972800,62704844800, 147220070400] |