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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 12 |
| 5 | 40 |
| 6 | 195 |
| 7 | 861 |
| 8 | 5488 |
| 9 | 31032 |
| 10 | 247005 |
| 11 | 1706815 |
| 12 | 16302396 |
| 13 | 133131648 |
| 14 | 1483518127 |
| 15 | 13978823145 |
| 16 | 178022175360 |
| 17 | 1901119947856 |
| 18 | 27237392830233 |
| 19 | 325091511083547 |
| 20 | 5175104637744460 |
| 21 | 68269217327545080 |
| 22 | 1195449171318970491 |
[0,1,3,12,40,195,861,5488,31032,247005,1706815, 16302396,133131648,1483518127,13978823145, 178022175360,1901119947856,27237392830233, 325091511083547,5175104637744460, 68269217327545080,1195449171318970491] |