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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 7 |
| 5 | 20 |
| 6 | 62 |
| 7 | 228 |
| 8 | 867 |
| 9 | 3474 |
| 10 | 14864 |
| 11 | 67101 |
| 12 | 316028 |
| 13 | 1540782 |
| 14 | 7792810 |
| 15 | 40669011 |
| 16 | 218087867 |
| 17 | 1201778736 |
| 18 | 6792071574 |
| 19 | 39309770969 |
| 20 | 232718797430 |
| 21 | 1407837227275 |
| 22 | 8694994837673 |
| 23 | 54771751869237 |
| 24 | 351643945379956 |
| 25 | 2299330292987022 |
| 26 | 15302662859459784 |
[1,1,1,2,7,20,62,228,867,3474,14864,67101,316028, 1540782,7792810,40669011,218087867,1201778736, 6792071574,39309770969,232718797430,1407837227275, 8694994837673,54771751869237,351643945379956, 2299330292987022,15302662859459784] |