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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 6 |
| 3 | 51 |
| 4 | 578 |
| 5 | 7011 |
| 6 | 89931 |
| 7 | 1198798 |
| 8 | 16445122 |
| 9 | 230643888 |
| 10 | 3292247673 |
| 11 | 47672499727 |
| 12 | 698569117499 |
| 13 | 10339672571689 |
| 14 | 154357100458366 |
| 15 | 2321475460350492 |
| 16 | 35140713973159266 |
| 17 | 534971413383669580 |
| 18 | 8185501429052369700 |
| 19 | 125811555778930237392 |
| 20 | 1941590759206061655069 |
[1,0,6,51,578,7011,89931,1198798,16445122, 230643888,3292247673,47672499727,698569117499, 10339672571689,154357100458366,2321475460350492, 35140713973159266,534971413383669580, 8185501429052369700,125811555778930237392, 1941590759206061655069] |