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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 5 |
| 5 | 37 |
| 6 | 219 |
| 7 | 1823 |
| 8 | 13831 |
| 9 | 139879 |
| 10 | 1321535 |
| 11 | 15951919 |
| 12 | 181202031 |
| 13 | 2549722415 |
| 14 | 33883956911 |
| 15 | 545091050671 |
| 16 | 8301190456511 |
| 17 | 150332113604031 |
| 18 | 2581953013032639 |
[0,0,1,5,37,219,1823,13831,139879,1321535, 15951919,181202031,2549722415,33883956911, 545091050671,8301190456511,150332113604031, 2581953013032639] |