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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 45 |
| 3 | 369 |
| 4 | 2961 |
| 5 | 23697 |
| 6 | 189585 |
| 7 | 1516689 |
| 8 | 12133521 |
| 9 | 97068177 |
| 10 | 776545425 |
| 11 | 6212363409 |
| 12 | 49698907281 |
| 13 | 397591258257 |
| 14 | 3180730066065 |
| 15 | 25445840528529 |
| 16 | 203566724228241 |
| 17 | 1628533793825937 |
| 18 | 13028270350607505 |
| 19 | 104226162804860049 |
| 20 | 833809302438880401 |
| 21 | 6670474419511043217 |
| 22 | 53363795356088345745 |
[4,45,369,2961,23697,189585,1516689,12133521, 97068177,776545425,6212363409,49698907281, 397591258257,3180730066065,25445840528529, 203566724228241,1628533793825937, 13028270350607505,104226162804860049, 833809302438880401,6670474419511043217, 53363795356088345745] |