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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 10 |
| 4 | 46 |
| 5 | 166 |
| 6 | 856 |
| 7 | 3844 |
| 8 | 21820 |
| 9 | 114076 |
| 10 | 703216 |
| 11 | 4125496 |
| 12 | 27331624 |
| 13 | 175849480 |
| 14 | 1241782816 |
| 15 | 8627460976 |
| 16 | 64507687696 |
| 17 | 478625814544 |
| 18 | 3768517887040 |
| 19 | 29614311872416 |
| 20 | 244419831433696 |
| 21 | 2021278543778656 |
| 22 | 17419727924101504 |
[1,1,4,10,46,166,856,3844,21820,114076,703216, 4125496,27331624,175849480,1241782816,8627460976, 64507687696,478625814544,3768517887040, 29614311872416,244419831433696,2021278543778656, 17419727924101504] |