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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 24 |
| 3 | 252 |
| 4 | 3360 |
| 5 | 55008 |
| 6 | 1074816 |
| 7 | 24499968 |
| 8 | 639744000 |
| 9 | 18856765440 |
| 10 | 619897847808 |
| 11 | 22502300590080 |
| 12 | 894419152404480 |
| 13 | 38651030120693760 |
| 14 | 1804765006764441600 |
| 15 | 90574514900736933888 |
| 16 | 4862862027933962207232 |
| 17 | 278158492957848901779456 |
| 18 | 16889663645642083220324352 |
[1,3,24,252,3360,55008,1074816,24499968,639744000, 18856765440,619897847808,22502300590080, 894419152404480,38651030120693760, 1804765006764441600,90574514900736933888, 4862862027933962207232,278158492957848901779456, 16889663645642083220324352] |