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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 13 |
| 5 | 61 |
| 6 | 181 |
| 7 | 421 |
| 8 | 1261 |
| 9 | 5293 |
| 10 | 21421 |
| 11 | 73261 |
| 12 | 232321 |
| 13 | 789361 |
| 14 | 2954953 |
| 15 | 11127481 |
| 16 | 39961741 |
| 17 | 139908301 |
| 18 | 499315501 |
| 19 | 1835933293 |
| 20 | 6792310153 |
| 21 | 24827506873 |
| 22 | 90058277233 |
| 23 | 328509505633 |
| 24 | 1210097040769 |
| 25 | 4473191880961 |
| 26 | 16495696956961 |
| 27 | 60721903812961 |
[1,1,1,1,13,61,181,421,1261,5293,21421,73261, 232321,789361,2954953,11127481,39961741,139908301, 499315501,1835933293,6792310153,24827506873, 90058277233,328509505633,1210097040769, 4473191880961,16495696956961,60721903812961] |