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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 108 |
| 6 | 503 |
| 7 | 2385 |
| 8 | 11537 |
| 9 | 56992 |
| 10 | 286769 |
| 11 | 1464317 |
| 12 | 7564803 |
| 13 | 39457205 |
| 14 | 207500615 |
| 15 | 1099066181 |
| 16 | 5858206629 |
| 17 | 31399478619 |
| 18 | 169132215962 |
| 19 | 915057263082 |
| 20 | 4970445985138 |
| 21 | 27095859218337 |
| 22 | 148193424618950 |
| 23 | 812923791698402 |
| 24 | 4471543767583949 |
| 25 | 24657936277287687 |
[1,1,2,6,24,108,503,2385,11537,56992,286769, 1464317,7564803,39457205,207500615,1099066181, 5858206629,31399478619,169132215962,915057263082, 4970445985138,27095859218337,148193424618950, 812923791698402,4471543767583949, 24657936277287687] |