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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 23 |
| 5 | 106 |
| 6 | 568 |
| 7 | 3459 |
| 8 | 23544 |
| 9 | 176850 |
| 10 | 1451253 |
| 11 | 12904312 |
| 12 | 123489888 |
| 13 | 1264591561 |
| 14 | 13790277294 |
| 15 | 159466823794 |
| 16 | 1948259002647 |
| 17 | 25066729706582 |
| 18 | 338670605492700 |
| 19 | 4792623436607059 |
| 20 | 70873649458154500 |
| 21 | 1092969062435462254 |
| 22 | 17543703470388927229 |
| 23 | 292600906102204630092 |
[1,1,2,6,23,106,568,3459,23544,176850,1451253, 12904312,123489888,1264591561,13790277294, 159466823794,1948259002647,25066729706582, 338670605492700,4792623436607059, 70873649458154500,1092969062435462254, 17543703470388927229,292600906102204630092] |