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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 12 |
| 4 | 88 |
| 5 | 860 |
| 6 | 10392 |
| 7 | 149044 |
| 8 | 2478752 |
| 9 | 46875492 |
| 10 | 993291880 |
| 11 | 23311581524 |
| 12 | 600207989808 |
| 13 | 16820818373476 |
| 14 | 509711184710840 |
| 15 | 16606143020005620 |
| 16 | 578830045479469120 |
| 17 | 21493718211307208420 |
| 18 | 847057099952645864712 |
[1,1,2,12,88,860,10392,149044,2478752,46875492, 993291880,23311581524,600207989808,16820818373476, 509711184710840,16606143020005620, 578830045479469120,21493718211307208420, 847057099952645864712] |