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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 20 |
| 3 | 53 |
| 4 | 238 |
| 5 | 1102 |
| 6 | 5570 |
| 7 | 28594 |
| 8 | 149206 |
| 9 | 788373 |
| 10 | 4194079 |
| 11 | 22418762 |
| 12 | 120168046 |
| 13 | 645271922 |
| 14 | 3468733058 |
| 15 | 18659308842 |
| 16 | 100416125479 |
| 17 | 540536282078 |
| 18 | 2910157350115 |
| 19 | 15669370152621 |
| 20 | 84374942124034 |
| 21 | 454351598306349 |
[1,20,53,238,1102,5570,28594,149206,788373, 4194079,22418762,120168046,645271922,3468733058, 18659308842,100416125479,540536282078, 2910157350115,15669370152621,84374942124034, 454351598306349] |