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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 14 |
| 4 | 40 |
| 5 | 116 |
| 6 | 344 |
| 7 | 1016 |
| 8 | 2992 |
| 9 | 8816 |
| 10 | 25984 |
| 11 | 76576 |
| 12 | 225664 |
| 13 | 665024 |
| 14 | 1959808 |
| 15 | 5775488 |
| 16 | 17020160 |
| 17 | 50157824 |
| 18 | 147813376 |
| 19 | 435600896 |
| 20 | 1283700736 |
| 21 | 3783021568 |
| 22 | 11148433408 |
| 23 | 32854046720 |
| 24 | 96819736576 |
| 25 | 285324406784 |
| 26 | 840841134080 |
[1,4,14,40,116,344,1016,2992,8816,25984,76576, 225664,665024,1959808,5775488,17020160,50157824, 147813376,435600896,1283700736,3783021568, 11148433408,32854046720,96819736576,285324406784, 840841134080] |