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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 8 |
| 2 | 50 |
| 3 | 400 |
| 4 | 2402 |
| 5 | 19216 |
| 6 | 120100 |
| 7 | 960800 |
| 8 | 5764802 |
| 9 | 46118416 |
| 10 | 288240100 |
| 11 | 2305920800 |
| 12 | 13847054404 |
| 13 | 110776435232 |
| 14 | 692352720200 |
| 15 | 5538821761600 |
| 16 | 33232930569602 |
| 17 | 265863444556816 |
| 18 | 1661646528480100 |
| 19 | 13293172227840800 |
[1,8,50,400,2402,19216,120100,960800,5764802, 46118416,288240100,2305920800,13847054404, 110776435232,692352720200,5538821761600, 33232930569602,265863444556816,1661646528480100, 13293172227840800] |