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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 8 |
| 4 | 62 |
| 5 | 744 |
| 6 | 11102 |
| 7 | 201704 |
| 8 | 4323720 |
| 9 | 106591584 |
| 10 | 2974873656 |
| 11 | 92674125840 |
| 12 | 3188299718496 |
| 13 | 120053825169888 |
| 14 | 4911082489042992 |
| 15 | 216879763758962688 |
| 16 | 10283600782413709056 |
| 17 | 521088305671611058176 |
| 18 | 28101278301136842204288 |
| 19 | 1606968565080853531472640 |
[1,1,1,8,62,744,11102,201704,4323720,106591584, 2974873656,92674125840,3188299718496, 120053825169888,4911082489042992, 216879763758962688,10283600782413709056, 521088305671611058176,28101278301136842204288, 1606968565080853531472640] |