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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 13 |
| 5 | 61 |
| 6 | 289 |
| 7 | 1371 |
| 8 | 6505 |
| 9 | 30865 |
| 10 | 146449 |
| 11 | 694875 |
| 12 | 3297061 |
| 13 | 15643981 |
| 14 | 74227969 |
| 15 | 352198803 |
| 16 | 1671122065 |
| 17 | 7929183553 |
| 18 | 37622596897 |
| 19 | 178512678867 |
| 20 | 847011613885 |
| 21 | 4018922793661 |
| 22 | 19069089675553 |
| 23 | 90479513970219 |
[1,1,1,3,13,61,289,1371,6505,30865,146449,694875, 3297061,15643981,74227969,352198803,1671122065, 7929183553,37622596897,178512678867,847011613885, 4018922793661,19069089675553,90479513970219] |