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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 60 |
| 3 | 678 |
| 4 | 8076 |
| 5 | 99096 |
| 6 | 1239396 |
| 7 | 15709140 |
| 8 | 201078396 |
| 9 | 2593341768 |
| 10 | 33647629680 |
| 11 | 438693096870 |
| 12 | 5742698276340 |
| 13 | 75429886563336 |
| 14 | 993636177253080 |
| 15 | 13121886019508808 |
| 16 | 173664637285538268 |
| 17 | 2302815409326783720 |
| 18 | 30587580089238772176 |
| 19 | 406902359573509985784 |
| 20 | 5420349836578927206576 |
[1,6,60,678,8076,99096,1239396,15709140,201078396, 2593341768,33647629680,438693096870,5742698276340, 75429886563336,993636177253080,13121886019508808, 173664637285538268,2302815409326783720, 30587580089238772176,406902359573509985784, 5420349836578927206576] |