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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 24 |
| 5 | 86 |
| 6 | 328 |
| 7 | 1289 |
| 8 | 5180 |
| 9 | 21232 |
| 10 | 88384 |
| 11 | 372582 |
| 12 | 1587442 |
| 13 | 6825092 |
| 14 | 29573380 |
| 15 | 129014039 |
| 16 | 566183860 |
| 17 | 2497841196 |
| 18 | 11071594936 |
| 19 | 49281430216 |
| 20 | 220193658876 |
| 21 | 987234942328 |
| 22 | 4440142628200 |
| 23 | 20027079949202 |
| 24 | 90569211556534 |
[1,1,2,7,24,86,328,1289,5180,21232,88384,372582, 1587442,6825092,29573380,129014039,566183860, 2497841196,11071594936,49281430216,220193658876, 987234942328,4440142628200,20027079949202, 90569211556534] |