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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 10 |
| 4 | 33 |
| 5 | 81 |
| 6 | 282 |
| 7 | 762 |
| 8 | 2599 |
| 9 | 7979 |
| 10 | 27343 |
| 11 | 89371 |
| 12 | 315256 |
| 13 | 1078498 |
| 14 | 3857048 |
| 15 | 13651786 |
| 16 | 49475282 |
| 17 | 178736186 |
| 18 | 655247192 |
| 19 | 2401663838 |
| 20 | 8883371016 |
| 21 | 32906649488 |
| 22 | 122619768860 |
| 23 | 457836275272 |
| 24 | 1716620421629 |
| 25 | 6449729802639 |
| 26 | 24308647131627 |
| 27 | 91800114425437 |
[1,1,4,10,33,81,282,762,2599,7979,27343,89371, 315256,1078498,3857048,13651786,49475282, 178736186,655247192,2401663838,8883371016, 32906649488,122619768860,457836275272, 1716620421629,6449729802639,24308647131627, 91800114425437] |