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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 22 |
| 4 | 336 |
| 5 | 6006 |
| 6 | 117348 |
| 7 | 2428272 |
| 8 | 52303680 |
| 9 | 1160427510 |
| 10 | 26337699740 |
| 11 | 608642155660 |
| 12 | 14272471122560 |
| 13 | 338764038330480 |
| 14 | 8123136091556640 |
| 15 | 196484811079765440 |
| 16 | 4788469475873867520 |
| 17 | 117465323079289162230 |
| 18 | 2898183118626011393100 |
[1,2,22,336,6006,117348,2428272,52303680, 1160427510,26337699740,608642155660, 14272471122560,338764038330480,8123136091556640, 196484811079765440,4788469475873867520, 117465323079289162230,2898183118626011393100] |