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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 20 |
| 4 | 249 |
| 5 | 5087 |
| 6 | 155180 |
| 7 | 6609730 |
| 8 | 374548937 |
| 9 | 27237010543 |
| 10 | 2471980167855 |
| 11 | 273862966795982 |
| 12 | 36371476538686396 |
| 13 | 5704018487197135820 |
| 14 | 1042929404101002643300 |
| 15 | 219905097318369791869794 |
| 16 | 52967138256595856156574553 |
| 17 | 14453277961440111342752817767 |
[1,1,3,20,249,5087,155180,6609730,374548937, 27237010543,2471980167855,273862966795982, 36371476538686396,5704018487197135820, 1042929404101002643300,219905097318369791869794, 52967138256595856156574553, 14453277961440111342752817767] |