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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 8 |
| 3 | 40 |
| 4 | 128 |
| 5 | 1168 |
| 6 | 4448 |
| 7 | 66400 |
| 8 | 268544 |
| 9 | 6124480 |
| 10 | 25118336 |
| 11 | 827294848 |
| 12 | 3386501120 |
| 13 | 153439657216 |
| 14 | 624706655744 |
| 15 | 37378784384512 |
| 16 | 151446759993344 |
| 17 | 11573673369828352 |
| 18 | 46729404312578048 |
| 19 | 4439994292732364800 |
| 20 | 17884613664930529280 |
| 21 | 2067374053521268559872 |
[1,4,8,40,128,1168,4448,66400,268544,6124480, 25118336,827294848,3386501120,153439657216, 624706655744,37378784384512,151446759993344, 11573673369828352,46729404312578048, 4439994292732364800,17884613664930529280, 2067374053521268559872] |