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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 19 |
| 4 | 69 |
| 5 | 260 |
| 6 | 1044 |
| 7 | 4291 |
| 8 | 18222 |
| 9 | 78661 |
| 10 | 346083 |
| 11 | 1541366 |
| 12 | 6949629 |
| 13 | 31624846 |
| 14 | 145147357 |
| 15 | 670888223 |
| 16 | 3120523813 |
| 17 | 14593863806 |
| 18 | 68582232449 |
| 19 | 323676827232 |
| 20 | 1533444023240 |
| 21 | 7289712158895 |
| 22 | 34760673073594 |
| 23 | 166216482275935 |
| 24 | 796809625131341 |
| 25 | 3828527888555432 |
| 26 | 18433960812625851 |
| 27 | 88928010579621446 |
[1,2,6,19,69,260,1044,4291,18222,78661,346083, 1541366,6949629,31624846,145147357,670888223, 3120523813,14593863806,68582232449,323676827232, 1533444023240,7289712158895,34760673073594, 166216482275935,796809625131341,3828527888555432, 18433960812625851,88928010579621446] |