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| n | a(n) |
|---|---|
| 0 | 4 |
| 1 | 8 |
| 2 | 24 |
| 3 | 80 |
| 4 | 280 |
| 5 | 1008 |
| 6 | 3696 |
| 7 | 13728 |
| 8 | 51480 |
| 9 | 194480 |
| 10 | 739024 |
| 11 | 2821728 |
| 12 | 10816624 |
| 13 | 41602400 |
| 14 | 160466400 |
| 15 | 620470080 |
| 16 | 2404321560 |
| 17 | 9334424880 |
| 18 | 36300541200 |
| 19 | 141381055200 |
| 20 | 551386115280 |
| 21 | 2153031497760 |
| 22 | 8416395854880 |
| 23 | 32933722910400 |
| 24 | 128990414732400 |
[4,8,24,80,280,1008,3696,13728,51480,194480, 739024,2821728,10816624,41602400,160466400, 620470080,2404321560,9334424880,36300541200, 141381055200,551386115280,2153031497760, 8416395854880,32933722910400,128990414732400] |