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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 30 |
| 3 | 161 |
| 4 | 880 |
| 5 | 4779 |
| 6 | 26000 |
| 7 | 141474 |
| 8 | 769617 |
| 9 | 4187055 |
| 10 | 22779608 |
| 11 | 123930190 |
| 12 | 674233423 |
| 13 | 3668120119 |
| 14 | 19956134787 |
| 15 | 108569904387 |
| 16 | 590666693724 |
| 17 | 3213479157579 |
| 18 | 17482699850936 |
| 19 | 95113358094319 |
| 20 | 517457311408764 |
[4,30,161,880,4779,26000,141474,769617,4187055, 22779608,123930190,674233423,3668120119, 19956134787,108569904387,590666693724, 3213479157579,17482699850936,95113358094319, 517457311408764] |