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| n | a(n) |
|---|---|
| 1 | 3 |
| 2 | 21 |
| 3 | 144 |
| 4 | 1085 |
| 5 | 8685 |
| 6 | 72381 |
| 7 | 620420 |
| 8 | 5428680 |
| 9 | 48254941 |
| 10 | 434294481 |
| 11 | 3948131653 |
| 12 | 36191206824 |
| 13 | 334072678386 |
| 14 | 3102103442165 |
| 15 | 28952965460216 |
| 16 | 271434051189531 |
| 17 | 2554673422960304 |
| 18 | 24127471216847323 |
| 19 | 228576043106974645 |
| 20 | 2171472409516259137 |
| 21 | 20680689614440563220 |
[3,21,144,1085,8685,72381,620420,5428680,48254941, 434294481,3948131653,36191206824,334072678386, 3102103442165,28952965460216,271434051189531, 2554673422960304,24127471216847323, 228576043106974645,2171472409516259137, 20680689614440563220] |