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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 8 |
| 3 | 40 |
| 4 | 212 |
| 5 | 1152 |
| 6 | 6360 |
| 7 | 35520 |
| 8 | 200132 |
| 9 | 1135456 |
| 10 | 6478088 |
| 11 | 37128896 |
| 12 | 213617704 |
| 13 | 1233014720 |
| 14 | 7136819376 |
| 15 | 41408161920 |
| 16 | 240758343684 |
| 17 | 1402436532576 |
| 18 | 8182797500328 |
| 19 | 47814708577728 |
| 20 | 279768031296312 |
| 21 | 1638915078384960 |
| 22 | 9611453035886160 |
[1,2,8,40,212,1152,6360,35520,200132,1135456, 6478088,37128896,213617704,1233014720,7136819376, 41408161920,240758343684,1402436532576, 8182797500328,47814708577728,279768031296312, 1638915078384960,9611453035886160] |