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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 12 |
| 5 | 100 |
| 6 | 870 |
| 7 | 7588 |
| 8 | 73808 |
| 9 | 764524 |
| 10 | 8448120 |
| 11 | 103816944 |
| 12 | 1334764728 |
| 13 | 18483356736 |
| 14 | 274780501632 |
| 15 | 4371694872192 |
| 16 | 71815113008640 |
| 17 | 1282261138007040 |
| 18 | 23828058693642240 |
| 19 | 468231649812725760 |
| 20 | 9599857257164820480 |
| 21 | 205863214718290636800 |
| 22 | 4646428416182168985600 |
[0,0,1,12,100,870,7588,73808,764524,8448120, 103816944,1334764728,18483356736,274780501632, 4371694872192,71815113008640,1282261138007040, 23828058693642240,468231649812725760, 9599857257164820480,205863214718290636800, 4646428416182168985600] |