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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 8 |
| 3 | 30 |
| 4 | 120 |
| 5 | 504 |
| 6 | 2126 |
| 7 | 9170 |
| 8 | 40044 |
| 9 | 176044 |
| 10 | 781600 |
| 11 | 3490012 |
| 12 | 15664056 |
| 13 | 70669628 |
| 14 | 320004610 |
| 15 | 1454279906 |
| 16 | 6630320468 |
| 17 | 30309488628 |
| 18 | 138910831512 |
| 19 | 638073465476 |
| 20 | 2936860540160 |
| 21 | 13543141717064 |
| 22 | 62559629953436 |
| 23 | 289436485560372 |
| 24 | 1341060883889256 |
| 25 | 6221966893608856 |
| 26 | 28903711416385792 |
| 27 | 134427762081030024 |
[1,2,8,30,120,504,2126,9170,40044,176044,781600, 3490012,15664056,70669628,320004610,1454279906, 6630320468,30309488628,138910831512,638073465476, 2936860540160,13543141717064,62559629953436, 289436485560372,1341060883889256,6221966893608856, 28903711416385792,134427762081030024] |