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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 55 |
| 5 | 224 |
| 6 | 1054 |
| 7 | 4855 |
| 8 | 23764 |
| 9 | 116491 |
| 10 | 587824 |
| 11 | 2988264 |
| 12 | 15439018 |
| 13 | 80389938 |
| 14 | 422931343 |
| 15 | 2240237896 |
| 16 | 11953324634 |
| 17 | 64141694737 |
| 18 | 346092872529 |
| 19 | 1876152637561 |
| 20 | 10215165278984 |
| 21 | 55833837924973 |
| 22 | 306268569253825 |
| 23 | 1685420531789073 |
| 24 | 9302712249561453 |
| 25 | 51486848030764303 |
| 26 | 285680988543516211 |
[1,1,4,12,55,224,1054,4855,23764,116491,587824, 2988264,15439018,80389938,422931343,2240237896, 11953324634,64141694737,346092872529, 1876152637561,10215165278984,55833837924973, 306268569253825,1685420531789073,9302712249561453, 51486848030764303,285680988543516211] |