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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 9 |
| 4 | 41 |
| 5 | 244 |
| 6 | 1555 |
| 7 | 10037 |
| 8 | 68599 |
| 9 | 476981 |
| 10 | 3399518 |
| 11 | 24652718 |
| 12 | 181411439 |
| 13 | 1352123760 |
| 14 | 10185964435 |
| 15 | 77458698781 |
| 16 | 593871350009 |
| 17 | 4586247704944 |
| 18 | 35646681303447 |
| 19 | 278665636846853 |
| 20 | 2189789189667782 |
| 21 | 17288684906561300 |
| 22 | 137081212514315262 |
| 23 | 1091163063187762414 |
[1,1,1,9,41,244,1555,10037,68599,476981,3399518, 24652718,181411439,1352123760,10185964435, 77458698781,593871350009,4586247704944, 35646681303447,278665636846853,2189789189667782, 17288684906561300,137081212514315262, 1091163063187762414] |