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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 5 |
| 3 | 15 |
| 4 | 49 |
| 5 | 180 |
| 6 | 685 |
| 7 | 2748 |
| 8 | 11683 |
| 9 | 52262 |
| 10 | 245357 |
| 11 | 1207538 |
| 12 | 6217803 |
| 13 | 33428738 |
| 14 | 187323142 |
| 15 | 1092328063 |
| 16 | 6618105311 |
| 17 | 41600580908 |
| 18 | 270931087106 |
| 19 | 1825820975565 |
| 20 | 12716770294407 |
| 21 | 91437668751232 |
| 22 | 678020392413506 |
| 23 | 5179601279549207 |
[1,1,5,15,49,180,685,2748,11683,52262,245357, 1207538,6217803,33428738,187323142,1092328063, 6618105311,41600580908,270931087106,1825820975565, 12716770294407,91437668751232,678020392413506, 5179601279549207] |