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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 15 |
| 2 | 113 |
| 3 | 799 |
| 4 | 5601 |
| 5 | 39215 |
| 6 | 274513 |
| 7 | 1921599 |
| 8 | 13451201 |
| 9 | 94158415 |
| 10 | 659108913 |
| 11 | 4613762399 |
| 12 | 32296336801 |
| 13 | 226074357615 |
| 14 | 1582520503313 |
| 15 | 11077643523199 |
| 16 | 77543504662401 |
| 17 | 542804532636815 |
| 18 | 3799631728457713 |
| 19 | 26597422099203999 |
| 20 | 186181954694428001 |
[1,15,113,799,5601,39215,274513,1921599,13451201, 94158415,659108913,4613762399,32296336801, 226074357615,1582520503313,11077643523199, 77543504662401,542804532636815,3799631728457713, 26597422099203999,186181954694428001] |