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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 6 |
| 4 | 24 |
| 5 | 40 |
| 6 | 160 |
| 7 | 280 |
| 8 | 1120 |
| 9 | 2016 |
| 10 | 8064 |
| 11 | 14784 |
| 12 | 59136 |
| 13 | 109824 |
| 14 | 439296 |
| 15 | 823680 |
| 16 | 3294720 |
| 17 | 6223360 |
| 18 | 24893440 |
| 19 | 47297536 |
| 20 | 189190144 |
| 21 | 361181184 |
| 22 | 1444724736 |
| 23 | 2769055744 |
| 24 | 11076222976 |
| 25 | 21300428800 |
| 26 | 85201715200 |
| 27 | 164317593600 |
[1,1,4,6,24,40,160,280,1120,2016,8064,14784,59136, 109824,439296,823680,3294720,6223360,24893440, 47297536,189190144,361181184,1444724736, 2769055744,11076222976,21300428800,85201715200, 164317593600] |