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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 10 |
| 5 | 31 |
| 6 | 98 |
| 7 | 321 |
| 8 | 1078 |
| 9 | 3686 |
| 10 | 12789 |
| 11 | 44919 |
| 12 | 159407 |
| 13 | 570704 |
| 14 | 2058817 |
| 15 | 7476621 |
| 16 | 27310345 |
| 17 | 100275628 |
| 18 | 369886451 |
| 19 | 1370066394 |
| 20 | 5093778398 |
| 21 | 19002602171 |
| 22 | 71109895075 |
| 23 | 266855940177 |
| 24 | 1004045604976 |
| 25 | 3786790901401 |
| 26 | 14313706230574 |
| 27 | 54215799080454 |
[1,1,1,3,10,31,98,321,1078,3686,12789,44919, 159407,570704,2058817,7476621,27310345,100275628, 369886451,1370066394,5093778398,19002602171, 71109895075,266855940177,1004045604976, 3786790901401,14313706230574,54215799080454] |