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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 10 |
| 4 | 44 |
| 5 | 84 |
| 6 | 528 |
| 7 | 864 |
| 8 | 4944 |
| 9 | 12720 |
| 10 | 56832 |
| 11 | 89856 |
| 12 | 882432 |
| 13 | 1209600 |
| 14 | 6036480 |
| 15 | 20017152 |
| 16 | 98592768 |
| 17 | 141834240 |
| 18 | 1202135040 |
| 19 | 1625702400 |
| 20 | 12997877760 |
| 21 | 35291013120 |
| 22 | 124429271040 |
| 23 | 191102976000 |
| 24 | 2350327726080 |
| 25 | 4064999178240 |
| 26 | 15972386734080 |
| 27 | 47163577466880 |
[1,1,4,10,44,84,528,864,4944,12720,56832,89856, 882432,1209600,6036480,20017152,98592768, 141834240,1202135040,1625702400,12997877760, 35291013120,124429271040,191102976000, 2350327726080,4064999178240,15972386734080, 47163577466880] |