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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 8 |
| 3 | 72 |
| 4 | 450 |
| 5 | 3200 |
| 6 | 21632 |
| 7 | 149058 |
| 8 | 1019592 |
| 9 | 6993800 |
| 10 | 47922050 |
| 11 | 328499712 |
| 12 | 2251473408 |
| 13 | 15432082562 |
| 14 | 105772401800 |
| 15 | 724976569800 |
| 16 | 4969058770242 |
| 17 | 34058447431808 |
| 18 | 233440040239232 |
| 19 | 1600021920672450 |
| 20 | 10966713178192200 |
[2,8,72,450,3200,21632,149058,1019592,6993800, 47922050,328499712,2251473408,15432082562, 105772401800,724976569800,4969058770242, 34058447431808,233440040239232,1600021920672450, 10966713178192200] |