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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 7 |
| 5 | 31 |
| 6 | 121 |
| 7 | 806 |
| 8 | 5706 |
| 9 | 40902 |
| 10 | 345444 |
| 11 | 3627834 |
| 12 | 44916840 |
| 13 | 473882124 |
| 14 | 5607925896 |
| 15 | 73429902300 |
| 16 | 1169960275680 |
| 17 | 18289685306640 |
| 18 | 315392669158416 |
| 19 | 5046227338720884 |
| 20 | 98328156602878800 |
| 21 | 1862418125263338720 |
| 22 | 36536960773307025360 |
| 23 | 777453614193997039320 |
[1,1,1,1,7,31,121,806,5706,40902,345444,3627834, 44916840,473882124,5607925896,73429902300, 1169960275680,18289685306640,315392669158416, 5046227338720884,98328156602878800, 1862418125263338720,36536960773307025360, 777453614193997039320] |