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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 6 |
| 4 | 20 |
| 5 | 57 |
| 6 | 194 |
| 7 | 650 |
| 8 | 2287 |
| 9 | 8247 |
| 10 | 30240 |
| 11 | 113165 |
| 12 | 429076 |
| 13 | 1647654 |
| 14 | 6395755 |
| 15 | 25060015 |
| 16 | 98980363 |
| 17 | 393905643 |
| 18 | 1577464918 |
| 19 | 6354456606 |
| 20 | 25732494494 |
| 21 | 104690838017 |
| 22 | 427789036689 |
| 23 | 1754877559797 |
| 24 | 7224755292423 |
| 25 | 29843212323269 |
| 26 | 123647788677744 |
| 27 | 513754501188089 |
| 28 | 2140248310019905 |
[1,1,3,6,20,57,194,650,2287,8247,30240,113165, 429076,1647654,6395755,25060015,98980363, 393905643,1577464918,6354456606,25732494494, 104690838017,427789036689,1754877559797, 7224755292423,29843212323269,123647788677744, 513754501188089,2140248310019905] |