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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 12 |
| 4 | 124 |
| 5 | 1800 |
| 6 | 33654 |
| 7 | 769664 |
| 8 | 20811960 |
| 9 | 649520640 |
| 10 | 22977857130 |
| 11 | 908626363392 |
| 12 | 39716055829044 |
| 13 | 1901448823572480 |
| 14 | 98954978833285470 |
| 15 | 5562010902732226560 |
| 16 | 335794917699707735664 |
| 17 | 21671616664285622599680 |
| 18 | 1488915133606275294428370 |
| 19 | 108495148653912606138040320 |
[1,2,12,124,1800,33654,769664,20811960,649520640, 22977857130,908626363392,39716055829044, 1901448823572480,98954978833285470, 5562010902732226560,335794917699707735664, 21671616664285622599680,1488915133606275294428370, 108495148653912606138040320] |