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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 10 |
| 4 | 32 |
| 5 | 112 |
| 6 | 400 |
| 7 | 1464 |
| 8 | 5520 |
| 9 | 21296 |
| 10 | 83456 |
| 11 | 331136 |
| 12 | 1328320 |
| 13 | 5379200 |
| 14 | 21959936 |
| 15 | 90271904 |
| 16 | 373347840 |
| 17 | 1552438016 |
| 18 | 6486311680 |
| 19 | 27217331456 |
| 20 | 114649525760 |
| 21 | 484640538112 |
| 22 | 2055185596416 |
| 23 | 8740711936000 |
| 24 | 37273693649920 |
| 25 | 159340373710848 |
| 26 | 682708771254272 |
| 27 | 2931290431277056 |
[1,2,4,10,32,112,400,1464,5520,21296,83456,331136, 1328320,5379200,21959936,90271904,373347840, 1552438016,6486311680,27217331456,114649525760, 484640538112,2055185596416,8740711936000, 37273693649920,159340373710848,682708771254272, 2931290431277056] |