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| n | a(n) |
|---|---|
| 3 | 1 |
| 4 | 0 |
| 5 | 0 |
| 6 | 20 |
| 7 | 70 |
| 8 | 112 |
| 9 | 1848 |
| 10 | 12840 |
| 11 | 62700 |
| 12 | 591800 |
| 13 | 5484908 |
| 14 | 40589276 |
| 15 | 421291780 |
| 16 | 4704380800 |
| 17 | 46345716880 |
| 18 | 533446290384 |
| 19 | 6931113219780 |
| 20 | 85313661653400 |
| 21 | 1121432682942740 |
| 22 | 16310909250477380 |
| 23 | 237534778732260548 |
| 24 | 3578871132644512672 |
| 25 | 57980168196079811800 |
[1,0,0,20,70,112,1848,12840,62700,591800,5484908, 40589276,421291780,4704380800,46345716880, 533446290384,6931113219780,85313661653400, 1121432682942740,16310909250477380, 237534778732260548,3578871132644512672, 57980168196079811800] |