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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 20 |
| 3 | 57 |
| 4 | 126 |
| 5 | 700 |
| 6 | 2569 |
| 7 | 7779 |
| 8 | 31081 |
| 9 | 117084 |
| 10 | 400727 |
| 11 | 1478944 |
| 12 | 5485580 |
| 13 | 19599269 |
| 14 | 71231855 |
| 15 | 261062287 |
| 16 | 945122754 |
| 17 | 3430304343 |
| 18 | 12504256178 |
| 19 | 45424857782 |
| 20 | 164983194009 |
| 21 | 600231458537 |
| 22 | 2182009835511 |
| 23 | 7929300624520 |
| 24 | 28830589829675 |
[1,20,57,126,700,2569,7779,31081,117084,400727, 1478944,5485580,19599269,71231855,261062287, 945122754,3430304343,12504256178,45424857782, 164983194009,600231458537,2182009835511, 7929300624520,28830589829675] |