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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 30 |
| 5 | 324 |
| 6 | 4480 |
| 7 | 74544 |
| 8 | 1438808 |
| 9 | 31459536 |
| 10 | 766573668 |
| 11 | 20569553080 |
| 12 | 602290243456 |
| 13 | 19105119410064 |
| 14 | 652635503205608 |
| 15 | 23888307843434944 |
| 16 | 932847459551529600 |
| 17 | 38716407912891973504 |
| 18 | 1702050349577155752784 |
| 19 | 79018450946973490981176 |
[1,1,4,30,324,4480,74544,1438808,31459536, 766573668,20569553080,602290243456,19105119410064, 652635503205608,23888307843434944, 932847459551529600,38716407912891973504, 1702050349577155752784,79018450946973490981176] |