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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 5 |
| 3 | 15 |
| 4 | 61 |
| 5 | 308 |
| 6 | 1851 |
| 7 | 12959 |
| 8 | 103678 |
| 9 | 933103 |
| 10 | 9331039 |
| 11 | 102641438 |
| 12 | 1231697258 |
| 13 | 16012064360 |
| 14 | 224168901043 |
| 15 | 3362533515646 |
| 16 | 53800536250343 |
| 17 | 914609116255840 |
| 18 | 16462964092605136 |
| 19 | 312796317759497601 |
| 20 | 6255926355189952031 |
[2,5,15,61,308,1851,12959,103678,933103,9331039, 102641438,1231697258,16012064360,224168901043, 3362533515646,53800536250343,914609116255840, 16462964092605136,312796317759497601, 6255926355189952031] |