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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 0 |
| 3 | 10 |
| 4 | 60 |
| 5 | 505 |
| 6 | 3876 |
| 7 | 33125 |
| 8 | 290700 |
| 9 | 2661100 |
| 10 | 25049020 |
| 11 | 241724375 |
| 12 | 2379812100 |
| 13 | 23833198135 |
| 14 | 242172147380 |
| 15 | 2491817140380 |
| 16 | 25921361665100 |
| 17 | 272256630756260 |
| 18 | 2884054853862540 |
| 19 | 30784716141936520 |
| 20 | 330853931834416520 |
| 21 | 3577823885432126890 |
| 22 | 38907658110093347780 |
[1,1,0,10,60,505,3876,33125,290700,2661100, 25049020,241724375,2379812100,23833198135, 242172147380,2491817140380,25921361665100, 272256630756260,2884054853862540, 30784716141936520,330853931834416520, 3577823885432126890,38907658110093347780] |