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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 12 |
| 4 | 40 |
| 5 | 128 |
| 6 | 400 |
| 7 | 1248 |
| 8 | 3904 |
| 9 | 12224 |
| 10 | 38272 |
| 11 | 119808 |
| 12 | 375040 |
| 13 | 1174016 |
| 14 | 3675136 |
| 15 | 11504640 |
| 16 | 36014080 |
| 17 | 112738304 |
| 18 | 352915456 |
| 19 | 1104764928 |
| 20 | 3458351104 |
| 21 | 10826006528 |
| 22 | 33889681408 |
| 23 | 106088103936 |
| 24 | 332097716224 |
| 25 | 1039597174784 |
[1,2,4,12,40,128,400,1248,3904,12224,38272,119808, 375040,1174016,3675136,11504640,36014080, 112738304,352915456,1104764928,3458351104, 10826006528,33889681408,106088103936,332097716224, 1039597174784] |