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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 10 |
| 4 | 28 |
| 5 | 84 |
| 6 | 264 |
| 7 | 858 |
| 8 | 2860 |
| 9 | 9724 |
| 10 | 33592 |
| 11 | 117572 |
| 12 | 416024 |
| 13 | 1485800 |
| 14 | 5348880 |
| 15 | 19389690 |
| 16 | 70715340 |
| 17 | 259289580 |
| 18 | 955277400 |
| 19 | 3534526380 |
| 20 | 13128240840 |
| 21 | 48932534040 |
| 22 | 182965127280 |
| 23 | 686119227300 |
| 24 | 2579808294648 |
| 25 | 9723892802904 |
[1,2,4,10,28,84,264,858,2860,9724,33592,117572, 416024,1485800,5348880,19389690,70715340, 259289580,955277400,3534526380,13128240840, 48932534040,182965127280,686119227300, 2579808294648,9723892802904] |