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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 12 |
| 4 | 96 |
| 5 | 320 |
| 6 | 3840 |
| 7 | 161280 |
| 8 | 516096 |
| 9 | 46448640 |
| 10 | 185794560 |
| 11 | 2270822400 |
| 12 | 163499212800 |
| 13 | 1821848371200 |
| 14 | 51011754393600 |
| 15 | 10712468422656000 |
| 16 | 9794256843571200 |
| 17 | 555007887802368000 |
| 18 | 139861987726196736000 |
| 19 | 1449478781889675264000 |
| 20 | 49059281848573624320000 |
[1,1,12,96,320,3840,161280,516096,46448640, 185794560,2270822400,163499212800,1821848371200, 51011754393600,10712468422656000,9794256843571200, 555007887802368000,139861987726196736000, 1449478781889675264000,49059281848573624320000] |