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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 3 |
| 3 | 18 |
| 4 | 91 |
| 5 | 420 |
| 6 | 1829 |
| 7 | 7686 |
| 8 | 31623 |
| 9 | 128520 |
| 10 | 518665 |
| 11 | 2084874 |
| 12 | 8361995 |
| 13 | 33497100 |
| 14 | 134094861 |
| 15 | 536608782 |
| 16 | 2146926607 |
| 17 | 8588754960 |
| 18 | 34357248017 |
| 19 | 137433710610 |
| 20 | 549744803859 |
| 21 | 2199000186900 |
| 22 | 8796044787733 |
| 23 | 35184271425558 |
| 24 | 140737278640151 |
| 25 | 562949517213720 |
[0,3,18,91,420,1829,7686,31623,128520,518665, 2084874,8361995,33497100,134094861,536608782, 2146926607,8588754960,34357248017,137433710610, 549744803859,2199000186900,8796044787733, 35184271425558,140737278640151,562949517213720] |