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| n | a(n) |
|---|---|
| 1 | 15 |
| 2 | 225 |
| 3 | 2111 |
| 4 | 14123 |
| 5 | 74040 |
| 6 | 323394 |
| 7 | 1226491 |
| 8 | 4157102 |
| 9 | 12856218 |
| 10 | 36834899 |
| 11 | 98904313 |
| 12 | 251078009 |
| 13 | 606789828 |
| 14 | 1403779390 |
| 15 | 3122765753 |
| 16 | 6704628063 |
| 17 | 13936852281 |
| 18 | 28123662137 |
| 19 | 55220811463 |
| 20 | 105715542647 |
| 21 | 197678421680 |
[15,225,2111,14123,74040,323394,1226491,4157102, 12856218,36834899,98904313,251078009,606789828, 1403779390,3122765753,6704628063,13936852281, 28123662137,55220811463,105715542647,197678421680] |