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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 16 |
| 5 | 54 |
| 6 | 192 |
| 7 | 720 |
| 8 | 2703 |
| 9 | 10516 |
| 10 | 41705 |
| 11 | 168001 |
| 12 | 689349 |
| 13 | 2859808 |
| 14 | 12006070 |
| 15 | 50816519 |
| 16 | 217011153 |
| 17 | 932736893 |
| 18 | 4035832654 |
| 19 | 17565418331 |
| 20 | 76834165053 |
| 21 | 337790073171 |
| 22 | 1491128371657 |
| 23 | 6609622369168 |
| 24 | 29400175070022 |
| 25 | 131221249915403 |
| 26 | 587446331571253 |
| 27 | 2637383430625903 |
| 28 | 11872227572864716 |
[1,1,2,5,16,54,192,720,2703,10516,41705,168001, 689349,2859808,12006070,50816519,217011153, 932736893,4035832654,17565418331,76834165053, 337790073171,1491128371657,6609622369168, 29400175070022,131221249915403,587446331571253, 2637383430625903,11872227572864716] |