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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 4 |
| 5 | 10 |
| 6 | 20 |
| 7 | 35 |
| 8 | 3976 |
| 9 | 35364 |
| 10 | 205920 |
| 11 | 970365 |
| 12 | 37643980 |
| 13 | 670990606 |
| 14 | 7705037704 |
| 15 | 69043474955 |
| 16 | 1690055888080 |
| 17 | 43135620048200 |
| 18 | 793592298255936 |
| 19 | 11401734214307769 |
| 20 | 250361353418216340 |
| 21 | 7380072768323315410 |
| 22 | 187670442928777057480 |
| 23 | 3868359812089009616071 |
[1,0,0,0,4,10,20,35,3976,35364,205920,970365, 37643980,670990606,7705037704,69043474955, 1690055888080,43135620048200,793592298255936, 11401734214307769,250361353418216340, 7380072768323315410,187670442928777057480, 3868359812089009616071] |