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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 5 |
| 2 | 20 |
| 3 | 73 |
| 4 | 225 |
| 5 | 821 |
| 6 | 3393 |
| 7 | 13237 |
| 8 | 51917 |
| 9 | 208729 |
| 10 | 831621 |
| 11 | 3320717 |
| 12 | 13275041 |
| 13 | 53058829 |
| 14 | 212174241 |
| 15 | 848720465 |
[1,5,20,73,225,821,3393,13237,51917,208729,831621, 3320717,13275041,53058829,212174241,848720465] |