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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 8 |
| 5 | 64 |
| 6 | 504 |
| 7 | 4132 |
| 8 | 36224 |
| 9 | 343197 |
| 10 | 3528800 |
| 11 | 39382654 |
| 12 | 476015616 |
| 13 | 6209617492 |
| 14 | 87072877696 |
| 15 | 1307012632486 |
| 16 | 20918494920704 |
| 17 | 355658666311252 |
| 18 | 6402175346437632 |
| 19 | 121643693845767057 |
| 20 | 2432891768176640000 |
| 21 | 51090865734892274539 |
| 22 | 1124000143459306268672 |
[0,0,0,0,8,64,504,4132,36224,343197,3528800, 39382654,476015616,6209617492,87072877696, 1307012632486,20918494920704,355658666311252, 6402175346437632,121643693845767057, 2432891768176640000,51090865734892274539, 1124000143459306268672] |