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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 12 |
| 5 | 24 |
| 6 | 60 |
| 7 | 140 |
| 8 | 315 |
| 9 | 756 |
| 10 | 1728 |
| 11 | 4032 |
| 12 | 9408 |
| 13 | 21756 |
| 14 | 50764 |
| 15 | 117845 |
| 16 | 273910 |
| 17 | 637260 |
| 18 | 1480404 |
| 19 | 3442800 |
| 20 | 8003000 |
| 21 | 18603000 |
| 22 | 43251975 |
| 23 | 100540440 |
| 24 | 233735040 |
| 25 | 543371136 |
| 26 | 1263161472 |
| 27 | 2936540824 |
| 28 | 6826574552 |
| 29 | 15869878969 |
| 30 | 36893076570 |
[1,2,4,12,24,60,140,315,756,1728,4032,9408,21756, 50764,117845,273910,637260,1480404,3442800, 8003000,18603000,43251975,100540440,233735040, 543371136,1263161472,2936540824,6826574552, 15869878969,36893076570] |