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| n | a(n) |
|---|---|
| 1 | 66 |
| 2 | 408 |
| 3 | 2988 |
| 4 | 20640 |
| 5 | 149120 |
| 6 | 1050624 |
| 7 | 7557696 |
| 8 | 53547904 |
| 9 | 384685440 |
| 10 | 2730236928 |
| 11 | 19605861888 |
| 12 | 139221963776 |
| 13 | 999628996096 |
| 14 | 7099542437888 |
| 15 | 50973532015616 |
| 16 | 362040887361536 |
| 17 | 2599362561034240 |
| 18 | 18462321529880576 |
| 19 | 132554347340582912 |
[66,408,2988,20640,149120,1050624,7557696, 53547904,384685440,2730236928,19605861888, 139221963776,999628996096,7099542437888, 50973532015616,362040887361536,2599362561034240, 18462321529880576,132554347340582912] |