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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 8 |
| 2 | 56 |
| 3 | 384 |
| 4 | 2640 |
| 5 | 18304 |
| 6 | 128128 |
| 7 | 905216 |
| 8 | 6449664 |
| 9 | 46305280 |
| 10 | 334721024 |
| 11 | 2434334720 |
| 12 | 17801072640 |
| 13 | 130809692160 |
| 14 | 965500108800 |
| 15 | 7154863964160 |
| 16 | 53214300733440 |
| 17 | 397094950010880 |
| 18 | 2972195534929920 |
| 19 | 22308469918924800 |
[1,8,56,384,2640,18304,128128,905216,6449664, 46305280,334721024,2434334720,17801072640, 130809692160,965500108800,7154863964160, 53214300733440,397094950010880,2972195534929920, 22308469918924800] |