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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 3 |
| 3 | 15 |
| 4 | 55 |
| 5 | 183 |
| 6 | 588 |
| 7 | 1865 |
| 8 | 5887 |
| 9 | 18550 |
| 10 | 58414 |
| 11 | 183904 |
| 12 | 578936 |
| 13 | 1822459 |
| 14 | 5736946 |
| 15 | 18059358 |
| 16 | 56849069 |
| 17 | 178955165 |
| 18 | 563332829 |
| 19 | 1773314909 |
| 20 | 5582216334 |
| 21 | 17572253459 |
| 22 | 55315679765 |
| 23 | 174128175040 |
| 24 | 548137914348 |
| 25 | 1725482812062 |
[0,3,15,55,183,588,1865,5887,18550,58414,183904, 578936,1822459,5736946,18059358,56849069, 178955165,563332829,1773314909,5582216334, 17572253459,55315679765,174128175040,548137914348, 1725482812062] |