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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 30 |
| 3 | 510 |
| 4 | 12240 |
| 5 | 379440 |
| 6 | 14418720 |
| 7 | 648842400 |
| 8 | 33739804800 |
| 9 | 1990648483200 |
| 10 | 131382799891200 |
| 11 | 9590944392057600 |
| 12 | 767275551364608000 |
| 13 | 66752972968720896000 |
| 14 | 6274779459059764224000 |
| 15 | 633752725365036186624000 |
| 16 | 68445294339423908155392000 |
| 17 | 7871208849033749437870080000 |
[1,3,30,510,12240,379440,14418720,648842400, 33739804800,1990648483200,131382799891200, 9590944392057600,767275551364608000, 66752972968720896000,6274779459059764224000, 633752725365036186624000, 68445294339423908155392000, 7871208849033749437870080000] |