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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 12 |
| 3 | 96 |
| 4 | 880 |
| 5 | 8736 |
| 6 | 91392 |
| 7 | 992256 |
| 8 | 11075328 |
| 9 | 126297600 |
| 10 | 1465052160 |
| 11 | 17233182720 |
| 12 | 205074874368 |
| 13 | 2464404045824 |
| 14 | 29864206663680 |
| 15 | 364535993597952 |
| 16 | 4477993284993024 |
| 17 | 55316387638149120 |
| 18 | 686720560048373760 |
| 19 | 8563155161736806400 |
| 20 | 107206525476085432320 |
[1,2,12,96,880,8736,91392,992256,11075328, 126297600,1465052160,17233182720,205074874368, 2464404045824,29864206663680,364535993597952, 4477993284993024,55316387638149120, 686720560048373760,8563155161736806400, 107206525476085432320] |