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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 20 |
| 5 | 73 |
| 6 | 281 |
| 7 | 1124 |
| 8 | 4618 |
| 9 | 19387 |
| 10 | 82765 |
| 11 | 358245 |
| 12 | 1568458 |
| 13 | 6933765 |
| 14 | 30907194 |
| 15 | 138760603 |
| 16 | 626898401 |
| 17 | 2847946941 |
| 18 | 13001772692 |
| 19 | 59618918444 |
| 20 | 274463781371 |
| 21 | 1268064807409 |
| 22 | 5877758070220 |
| 23 | 27325789128330 |
| 24 | 127384553264327 |
| 25 | 595318139942874 |
| 26 | 2788598203340643 |
| 27 | 13090395266913748 |
| 28 | 61571972632103632 |
[1,1,2,6,20,73,281,1124,4618,19387,82765,358245, 1568458,6933765,30907194,138760603,626898401, 2847946941,13001772692,59618918444,274463781371, 1268064807409,5877758070220,27325789128330, 127384553264327,595318139942874,2788598203340643, 13090395266913748,61571972632103632] |