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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 10 |
| 3 | 27 |
| 4 | 426 |
| 5 | 1847 |
| 6 | 16440 |
| 7 | 84558 |
| 8 | 910358 |
| 9 | 4757427 |
| 10 | 51324484 |
| 11 | 271866564 |
| 12 | 2984245628 |
| 13 | 15890235207 |
| 14 | 175650675430 |
| 15 | 939482925840 |
| 16 | 10439882627616 |
| 17 | 56035969028768 |
| 18 | 625001788261676 |
| 19 | 3364621225556746 |
| 20 | 37635020888605163 |
[4,10,27,426,1847,16440,84558,910358,4757427, 51324484,271866564,2984245628,15890235207, 175650675430,939482925840,10439882627616, 56035969028768,625001788261676,3364621225556746, 37635020888605163] |