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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 8 |
| 3 | 32 |
| 4 | 140 |
| 5 | 624 |
| 6 | 2928 |
| 7 | 14048 |
| 8 | 69200 |
| 9 | 347040 |
| 10 | 1768120 |
| 11 | 9122144 |
| 12 | 47572128 |
| 13 | 250341312 |
| 14 | 1327718272 |
| 15 | 7089595552 |
| 16 | 38082093120 |
| 17 | 205638343552 |
| 18 | 1115635692576 |
| 19 | 6078058719232 |
| 20 | 33239328613648 |
| 21 | 182402290944576 |
| 22 | 1004073853702320 |
[1,2,8,32,140,624,2928,14048,69200,347040,1768120, 9122144,47572128,250341312,1327718272,7089595552, 38082093120,205638343552,1115635692576, 6078058719232,33239328613648,182402290944576, 1004073853702320] |