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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 20 |
| 3 | 47 |
| 4 | 336 |
| 5 | 703 |
| 6 | 5440 |
| 7 | 11007 |
| 8 | 87296 |
| 9 | 175103 |
| 10 | 1397760 |
| 11 | 2797567 |
| 12 | 22368256 |
| 13 | 44744703 |
| 14 | 357908480 |
| 15 | 715849727 |
| 16 | 5726601216 |
| 17 | 11453333503 |
| 18 | 91625881600 |
| 19 | 183252287487 |
| 20 | 1466015154176 |
| 21 | 2932032405503 |
| 22 | 23456246661120 |
| 23 | 46912501710847 |
| 24 | 375299963355136 |
| 25 | 750599960264703 |
[1,3,20,47,336,703,5440,11007,87296,175103, 1397760,2797567,22368256,44744703,357908480, 715849727,5726601216,11453333503,91625881600, 183252287487,1466015154176,2932032405503, 23456246661120,46912501710847,375299963355136, 750599960264703] |