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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 7 |
| 3 | 56 |
| 4 | 392 |
| 5 | 3087 |
| 6 | 21952 |
| 7 | 170471 |
| 8 | 1210104 |
| 9 | 9411920 |
| 10 | 66824632 |
| 11 | 513890832 |
| 12 | 3683707839 |
| 13 | 28086110472 |
| 14 | 201122377288 |
| 15 | 1534688027817 |
| 16 | 10978118077136 |
| 17 | 83158453503608 |
| 18 | 599161640356888 |
| 19 | 4508826988300152 |
| 20 | 32435340235930576 |
| 21 | 244366486039786096 |
| 22 | 1756858874561956865 |
| 23 | 13161303959340223232 |
[1,1,7,56,392,3087,21952,170471,1210104,9411920, 66824632,513890832,3683707839,28086110472, 201122377288,1534688027817,10978118077136, 83158453503608,599161640356888,4508826988300152, 32435340235930576,244366486039786096, 1756858874561956865,13161303959340223232] |