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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 10 |
| 4 | 36 |
| 5 | 123 |
| 6 | 451 |
| 7 | 1715 |
| 8 | 6570 |
| 9 | 26133 |
| 10 | 104173 |
| 11 | 424824 |
| 12 | 1744847 |
| 13 | 7246790 |
| 14 | 30390296 |
| 15 | 128177201 |
| 16 | 545456346 |
| 17 | 2331067303 |
| 18 | 10029452264 |
| 19 | 43334144418 |
| 20 | 188114344033 |
| 21 | 820064019107 |
| 22 | 3587139466604 |
| 23 | 15751654599946 |
| 24 | 69360717243894 |
| 25 | 306415608927587 |
| 26 | 1357105949531911 |
| 27 | 6026355500018480 |
[1,1,4,10,36,123,451,1715,6570,26133,104173, 424824,1744847,7246790,30390296,128177201, 545456346,2331067303,10029452264,43334144418, 188114344033,820064019107,3587139466604, 15751654599946,69360717243894,306415608927587, 1357105949531911,6026355500018480] |