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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 10 |
| 4 | 40 |
| 5 | 296 |
| 6 | 1936 |
| 7 | 17872 |
| 8 | 164480 |
| 9 | 1820800 |
| 10 | 21442816 |
| 11 | 279255296 |
| 12 | 3967316992 |
| 13 | 59837670400 |
| 14 | 988024924160 |
| 15 | 17009993230336 |
| 16 | 318566665977856 |
| 17 | 6177885274406912 |
| 18 | 129053377688043520 |
| 19 | 2786107670662021120 |
| 20 | 64136976817284448256 |
| 21 | 1525720008470138454016 |
| 22 | 38350749144768938770432 |
[1,1,2,10,40,296,1936,17872,164480,1820800, 21442816,279255296,3967316992,59837670400, 988024924160,17009993230336,318566665977856, 6177885274406912,129053377688043520, 2786107670662021120,64136976817284448256, 1525720008470138454016,38350749144768938770432] |