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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 8 |
| 3 | 44 |
| 4 | 264 |
| 5 | 1632 |
| 6 | 10256 |
| 7 | 65200 |
| 8 | 418144 |
| 9 | 2700224 |
| 10 | 17534208 |
| 11 | 114380928 |
| 12 | 748988928 |
| 13 | 4920379648 |
| 14 | 32413343488 |
| 15 | 214038123264 |
| 16 | 1416349369856 |
| 17 | 9389756730368 |
| 18 | 62352450867200 |
| 19 | 414660440811520 |
| 20 | 2761261291024384 |
[1,2,8,44,264,1632,10256,65200,418144,2700224, 17534208,114380928,748988928,4920379648, 32413343488,214038123264,1416349369856, 9389756730368,62352450867200,414660440811520, 2761261291024384] |