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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 20 |
| 3 | 236 |
| 4 | 1678 |
| 5 | 9714 |
| 6 | 51229 |
| 7 | 251892 |
| 8 | 1144205 |
| 9 | 4762445 |
| 10 | 18164685 |
| 11 | 63838081 |
| 12 | 208288721 |
| 13 | 635843575 |
| 14 | 1829104046 |
| 15 | 4989647446 |
| 16 | 12978273537 |
| 17 | 32338548895 |
| 18 | 77506161543 |
| 19 | 179299342255 |
| 20 | 401569610694 |
| 21 | 873025241923 |
| 22 | 1846627291485 |
[0,20,236,1678,9714,51229,251892,1144205,4762445, 18164685,63838081,208288721,635843575,1829104046, 4989647446,12978273537,32338548895,77506161543, 179299342255,401569610694,873025241923, 1846627291485] |