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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 19 |
| 3 | 83 |
| 4 | 361 |
| 5 | 1574 |
| 6 | 6859 |
| 7 | 29898 |
| 8 | 130321 |
| 9 | 568056 |
| 10 | 2476099 |
| 11 | 10793065 |
| 12 | 47045881 |
| 13 | 205068241 |
| 14 | 893871739 |
| 15 | 3896296579 |
| 16 | 16983563041 |
| 17 | 74029634997 |
| 18 | 322687697779 |
| 19 | 1406563064942 |
| 20 | 6131066257801 |
| 21 | 26724698233907 |
[1,4,19,83,361,1574,6859,29898,130321,568056, 2476099,10793065,47045881,205068241,893871739, 3896296579,16983563041,74029634997,322687697779, 1406563064942,6131066257801,26724698233907] |