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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 4920 |
| 4 | 89955 |
| 5 | 977769 |
| 6 | 7670445 |
| 7 | 48447405 |
| 8 | 260865495 |
| 9 | 1241931125 |
| 10 | 5354625996 |
| 11 | 21268009665 |
| 12 | 78809488530 |
| 13 | 275102649810 |
| 14 | 911548565730 |
| 15 | 2884607044338 |
| 16 | 8761626447030 |
| 17 | 25649311876605 |
| 18 | 72623115075205 |
| 19 | 199467098107110 |
| 20 | 532810313084637 |
| 21 | 1387200530781195 |
[1,0,0,4920,89955,977769,7670445,48447405, 260865495,1241931125,5354625996,21268009665, 78809488530,275102649810,911548565730, 2884607044338,8761626447030,25649311876605, 72623115075205,199467098107110,532810313084637, 1387200530781195] |