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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 18 |
| 3 | 150 |
| 4 | 1546 |
| 5 | 18642 |
| 6 | 254690 |
| 7 | 3861782 |
| 8 | 64059002 |
| 9 | 1150296082 |
| 10 | 22180511810 |
| 11 | 456345207854 |
| 12 | 9966036502994 |
| 13 | 230031203755906 |
| 14 | 5591166290510722 |
| 15 | 142661974171422254 |
| 16 | 3810825154126609202 |
| 17 | 106314217107440685858 |
[1,3,18,150,1546,18642,254690,3861782,64059002, 1150296082,22180511810,456345207854,9966036502994, 230031203755906,5591166290510722, 142661974171422254,3810825154126609202, 106314217107440685858] |