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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 20 |
| 4 | 78 |
| 5 | 364 |
| 6 | 1758 |
| 7 | 9144 |
| 8 | 48508 |
| 9 | 264014 |
| 10 | 1457624 |
| 11 | 8158260 |
| 12 | 46134878 |
| 13 | 263312552 |
| 14 | 1514534512 |
| 15 | 8771202984 |
| 16 | 51101608190 |
| 17 | 299306977508 |
| 18 | 1761377916048 |
| 19 | 10409550718692 |
| 20 | 61755225688926 |
| 21 | 367639850029404 |
| 22 | 2195551697108888 |
| 23 | 13149811270786752 |
| 24 | 78967249613057836 |
| 25 | 475373797733460598 |
[1,2,6,20,78,364,1758,9144,48508,264014,1457624, 8158260,46134878,263312552,1514534512,8771202984, 51101608190,299306977508,1761377916048, 10409550718692,61755225688926,367639850029404, 2195551697108888,13149811270786752, 78967249613057836,475373797733460598] |