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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 4 |
| 3 | 18 |
| 4 | 74 |
| 5 | 1198 |
| 6 | 4794 |
| 7 | 76718 |
| 8 | 306874 |
| 9 | 4909998 |
| 10 | 314239934 |
| 11 | 1256959738 |
| 12 | 80445423294 |
| 13 | 1287126772718 |
| 14 | 5148507090874 |
| 15 | 82376113453998 |
| 16 | 5272071261055934 |
| 17 | 337412560707579838 |
| 18 | 1349650242830319354 |
| 19 | 86377615541140438718 |
| 20 | 1382041848658247019502 |
| 21 | 5528167394632988078010 |
[2,4,18,74,1198,4794,76718,306874,4909998, 314239934,1256959738,80445423294,1287126772718, 5148507090874,82376113453998,5272071261055934, 337412560707579838,1349650242830319354, 86377615541140438718,1382041848658247019502, 5528167394632988078010] |