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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 14 |
| 4 | 94 |
| 5 | 684 |
| 6 | 5508 |
| 7 | 49104 |
| 8 | 482256 |
| 9 | 5185440 |
| 10 | 60668640 |
| 11 | 767940480 |
| 12 | 10462227840 |
| 13 | 152698210560 |
| 14 | 2377651449600 |
| 15 | 39350097561600 |
| 16 | 689874448435200 |
| 17 | 12773427499929600 |
| 18 | 249097496204390400 |
| 19 | 5103595024496640000 |
| 20 | 109608397522606080000 |
[0,2,14,94,684,5508,49104,482256,5185440,60668640, 767940480,10462227840,152698210560,2377651449600, 39350097561600,689874448435200,12773427499929600, 249097496204390400,5103595024496640000, 109608397522606080000] |