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| n | a(n) |
|---|---|
| 0 | 2 |
| 1 | 2 |
| 2 | 3 |
| 3 | 5 |
| 4 | 10 |
| 5 | 22 |
| 6 | 54 |
| 7 | 142 |
| 8 | 402 |
| 9 | 1206 |
| 10 | 3810 |
| 11 | 12636 |
| 12 | 43776 |
| 13 | 157824 |
| 14 | 590520 |
| 15 | 2287080 |
| 16 | 9148320 |
| 17 | 37719360 |
| 18 | 160029696 |
| 19 | 697553280 |
| 20 | 3119552640 |
| 21 | 14295585696 |
| 22 | 67052240640 |
| 23 | 321571257120 |
| 24 | 1575370944000 |
| 25 | 7876854720000 |
| 26 | 40164235953600 |
[2,2,3,5,10,22,54,142,402,1206,3810,12636,43776, 157824,590520,2287080,9148320,37719360,160029696, 697553280,3119552640,14295585696,67052240640, 321571257120,1575370944000,7876854720000, 40164235953600] |