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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 6 |
| 5 | 35 |
| 6 | 221 |
| 7 | 1554 |
| 8 | 12108 |
| 9 | 104293 |
| 10 | 986452 |
| 11 | 10186669 |
| 12 | 114173261 |
| 13 | 1381606490 |
| 14 | 17963133122 |
| 15 | 249838334627 |
| 16 | 3702507093782 |
| 17 | 58255992451047 |
| 18 | 970036965428901 |
| 19 | 17043762930794782 |
| 20 | 315148172259643152 |
| 21 | 6117607922562556061 |
| 22 | 124394868793682972996 |
[0,0,1,6,35,221,1554,12108,104293,986452,10186669, 114173261,1381606490,17963133122,249838334627, 3702507093782,58255992451047,970036965428901, 17043762930794782,315148172259643152, 6117607922562556061,124394868793682972996] |