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| n | a(n) |
|---|---|
| 3 | 3 |
| 4 | 15 |
| 5 | 78 |
| 6 | 435 |
| 7 | 2658 |
| 8 | 18102 |
| 9 | 138780 |
| 10 | 1198971 |
| 11 | 11600730 |
| 12 | 124489794 |
| 13 | 1466798916 |
| 14 | 18807464910 |
| 15 | 260499759828 |
| 16 | 3874067519820 |
| 17 | 61547871299640 |
| 18 | 1040102328321675 |
| 19 | 18626778871389450 |
| 20 | 352351829564950410 |
[3,15,78,435,2658,18102,138780,1198971,11600730, 124489794,1466798916,18807464910,260499759828, 3874067519820,61547871299640,1040102328321675, 18626778871389450,352351829564950410] |