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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 40 |
| 4 | 15 |
| 5 | 451 |
| 6 | 160 |
| 7 | 4901 |
| 8 | 1785 |
| 9 | 55480 |
| 10 | 20295 |
| 11 | 630631 |
| 12 | 230400 |
| 13 | 7152809 |
| 14 | 2612233 |
| 15 | 81089800 |
| 16 | 29614935 |
| 17 | 919350379 |
| 18 | 335764960 |
| 19 | 10423396429 |
| 20 | 3806834625 |
| 21 | 118178205080 |
| 22 | 43161016271 |
| 23 | 1339876575119 |
| 24 | 489349324800 |
| 25 | 15191201606801 |
[1,1,1,40,15,451,160,4901,1785,55480,20295,630631, 230400,7152809,2612233,81089800,29614935, 919350379,335764960,10423396429,3806834625, 118178205080,43161016271,1339876575119, 489349324800,15191201606801] |