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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 15 |
| 5 | 103 |
| 6 | 829 |
| 7 | 7131 |
| 8 | 62901 |
| 9 | 559897 |
| 10 | 4999879 |
| 11 | 44699763 |
| 12 | 399783639 |
| 13 | 3576070333 |
| 14 | 31989586339 |
| 15 | 286166485929 |
| 16 | 2559950572641 |
| 17 | 22900519062931 |
| 18 | 204861053422423 |
| 19 | 1832624941137951 |
| 20 | 16394109244633845 |
| 21 | 146656754883677131 |
[1,1,3,15,103,829,7131,62901,559897,4999879, 44699763,399783639,3576070333,31989586339, 286166485929,2559950572641,22900519062931, 204861053422423,1832624941137951, 16394109244633845,146656754883677131] |