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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 4 |
| 3 | 4 |
| 4 | 16 |
| 5 | 64 |
| 6 | 196 |
| 7 | 676 |
| 8 | 2304 |
| 9 | 7744 |
| 10 | 26244 |
| 11 | 88804 |
| 12 | 300304 |
| 13 | 1016064 |
| 14 | 3437316 |
| 15 | 11628100 |
| 16 | 39337984 |
| 17 | 133079296 |
| 18 | 450203524 |
| 19 | 1523028676 |
| 20 | 5152368400 |
| 21 | 17430336576 |
| 22 | 58966408900 |
| 23 | 199481929956 |
| 24 | 674842534144 |
| 25 | 2282975946304 |
| 26 | 7723252297476 |
[0,4,4,16,64,196,676,2304,7744,26244,88804,300304, 1016064,3437316,11628100,39337984,133079296, 450203524,1523028676,5152368400,17430336576, 58966408900,199481929956,674842534144, 2282975946304,7723252297476] |