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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 22 |
| 5 | 90 |
| 6 | 396 |
| 7 | 1833 |
| 8 | 8801 |
| 9 | 43441 |
| 10 | 219092 |
| 11 | 1124201 |
| 12 | 5850414 |
| 13 | 30805498 |
| 14 | 163824559 |
| 15 | 878655117 |
| 16 | 4747341879 |
| 17 | 25815026491 |
| 18 | 141173582016 |
| 19 | 775920816789 |
| 20 | 4283833709457 |
| 21 | 23746640019657 |
| 22 | 132116647765569 |
| 23 | 737485227605338 |
| 24 | 4129174120158569 |
| 25 | 23183379592361839 |
[1,1,2,6,22,90,396,1833,8801,43441,219092,1124201, 5850414,30805498,163824559,878655117,4747341879, 25815026491,141173582016,775920816789, 4283833709457,23746640019657,132116647765569, 737485227605338,4129174120158569, 23183379592361839] |