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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 27 |
| 5 | 138 |
| 6 | 830 |
| 7 | 5813 |
| 8 | 46511 |
| 9 | 418605 |
| 10 | 4186056 |
| 11 | 46046623 |
| 12 | 552559478 |
| 13 | 7183273217 |
| 14 | 100565825043 |
| 15 | 1508487375646 |
| 16 | 24135798010342 |
| 17 | 410308566175816 |
| 18 | 7385554191164692 |
| 19 | 140325529632129156 |
| 20 | 2806510592642583123 |
[1,2,6,27,138,830,5813,46511,418605,4186056, 46046623,552559478,7183273217,100565825043, 1508487375646,24135798010342,410308566175816, 7385554191164692,140325529632129156, 2806510592642583123] |