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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 5 |
| 5 | 21 |
| 6 | 116 |
| 7 | 751 |
| 8 | 5628 |
| 9 | 47811 |
| 10 | 453999 |
| 11 | 4765190 |
| 12 | 54782415 |
| 13 | 684597510 |
| 14 | 9239952802 |
| 15 | 133952757201 |
| 16 | 2075907567336 |
| 17 | 34247231626810 |
| 18 | 599244998013964 |
| 19 | 11084682598687313 |
| 20 | 216127622080213321 |
[0,1,1,5,21,116,751,5628,47811,453999,4765190, 54782415,684597510,9239952802,133952757201, 2075907567336,34247231626810,599244998013964, 11084682598687313,216127622080213321] |