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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 16 |
| 5 | 80 |
| 6 | 480 |
| 7 | 3296 |
| 8 | 25152 |
| 9 | 209600 |
| 10 | 1884160 |
| 11 | 18110080 |
| 12 | 184898304 |
| 13 | 1994964736 |
| 14 | 22654449664 |
| 15 | 269855506944 |
| 16 | 3362350046208 |
| 17 | 43715434232832 |
| 18 | 591812683833344 |
| 19 | 8326660788725760 |
| 20 | 121550217508892672 |
| 21 | 1838089917983911936 |
| 22 | 28753297176215257088 |
| 23 | 464675647688625364992 |
[1,2,4,16,80,480,3296,25152,209600,1884160, 18110080,184898304,1994964736,22654449664, 269855506944,3362350046208,43715434232832, 591812683833344,8326660788725760, 121550217508892672,1838089917983911936, 28753297176215257088,464675647688625364992] |