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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 7 |
| 2 | 15 |
| 3 | 80 |
| 4 | 371 |
| 5 | 2088 |
| 6 | 11771 |
| 7 | 70305 |
| 8 | 427405 |
| 9 | 2663932 |
| 10 | 16853341 |
| 11 | 108166507 |
| 12 | 701904555 |
| 13 | 4599254190 |
| 14 | 30383303055 |
| 15 | 202154463130 |
| 16 | 1353408327935 |
| 17 | 9110887281150 |
| 18 | 61632613465475 |
| 19 | 418751976874065 |
| 20 | 2856336340630845 |
[1,7,15,80,371,2088,11771,70305,427405,2663932, 16853341,108166507,701904555,4599254190, 30383303055,202154463130,1353408327935, 9110887281150,61632613465475,418751976874065, 2856336340630845] |