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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 4 |
| 4 | 19 |
| 5 | 100 |
| 6 | 566 |
| 7 | 3384 |
| 8 | 21107 |
| 9 | 136084 |
| 10 | 900674 |
| 11 | 6087496 |
| 12 | 41850366 |
| 13 | 291766952 |
| 14 | 2057964492 |
| 15 | 14659421040 |
| 16 | 105305580483 |
| 17 | 761981900724 |
| 18 | 5548736343434 |
| 19 | 40632122219688 |
| 20 | 299017702596554 |
| 21 | 2210275626304248 |
| 22 | 16403005547059508 |
| 23 | 122169144755555088 |
| 24 | 912887876722311406 |
[0,0,1,4,19,100,566,3384,21107,136084,900674, 6087496,41850366,291766952,2057964492,14659421040, 105305580483,761981900724,5548736343434, 40632122219688,299017702596554,2210275626304248, 16403005547059508,122169144755555088, 912887876722311406] |