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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 13 |
| 5 | 56 |
| 6 | 277 |
| 7 | 1429 |
| 8 | 8489 |
| 9 | 51769 |
| 10 | 344961 |
| 11 | 2391698 |
| 12 | 17496661 |
| 13 | 133658565 |
| 14 | 1060426557 |
| 15 | 8749399966 |
| 16 | 74494928017 |
| 17 | 655734728718 |
| 18 | 5936865639625 |
| 19 | 55292734329958 |
| 20 | 528332681177821 |
| 21 | 5174197047357241 |
| 22 | 51867294310990885 |
| 23 | 531492968044248844 |
| 24 | 5562798258563207737 |
[1,1,1,4,13,56,277,1429,8489,51769,344961,2391698, 17496661,133658565,1060426557,8749399966, 74494928017,655734728718,5936865639625, 55292734329958,528332681177821,5174197047357241, 51867294310990885,531492968044248844, 5562798258563207737] |