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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 2 |
| 4 | 9 |
| 5 | 23 |
| 6 | 99 |
| 7 | 353 |
| 8 | 1778 |
| 9 | 7927 |
| 10 | 45273 |
| 11 | 238797 |
| 12 | 1526331 |
| 13 | 9215950 |
| 14 | 65020448 |
| 15 | 439742641 |
| 16 | 3388075807 |
| 17 | 25270974635 |
| 18 | 210763775071 |
| 19 | 1713657668021 |
| 20 | 15359474721088 |
| 21 | 134902169999841 |
| 22 | 1291589459223627 |
| 23 | 12165062702520422 |
| 24 | 123780591852786693 |
| 25 | 1242763745129587332 |
[1,0,2,2,9,23,99,353,1778,7927,45273,238797, 1526331,9215950,65020448,439742641,3388075807, 25270974635,210763775071,1713657668021, 15359474721088,134902169999841,1291589459223627, 12165062702520422,123780591852786693, 1242763745129587332] |