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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 20 |
| 4 | 73 |
| 5 | 286 |
| 6 | 1171 |
| 7 | 4930 |
| 8 | 21176 |
| 9 | 92591 |
| 10 | 411017 |
| 11 | 1846504 |
| 12 | 8372732 |
| 13 | 38262960 |
| 14 | 176083803 |
| 15 | 815325551 |
| 16 | 3795021644 |
| 17 | 17743531775 |
| 18 | 83289442421 |
| 19 | 392377483784 |
| 20 | 1854492950529 |
| 21 | 8790179694611 |
| 22 | 41772641587849 |
| 23 | 198979876476148 |
| 24 | 949875548782681 |
| 25 | 4543447373982078 |
| 26 | 21771657538903904 |
| 27 | 104501228825358146 |
[1,2,6,20,73,286,1171,4930,21176,92591,411017, 1846504,8372732,38262960,176083803,815325551, 3795021644,17743531775,83289442421,392377483784, 1854492950529,8790179694611,41772641587849, 198979876476148,949875548782681,4543447373982078, 21771657538903904,104501228825358146] |