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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 7 |
| 2 | 53 |
| 3 | 391 |
| 4 | 2865 |
| 5 | 20967 |
| 6 | 153413 |
| 7 | 1122471 |
| 8 | 8212705 |
| 9 | 60089287 |
| 10 | 439650773 |
| 11 | 3216759751 |
| 12 | 23535824145 |
| 13 | 172202794407 |
| 14 | 1259943234533 |
| 15 | 9218531904231 |
| 16 | 67448539061185 |
| 17 | 493495652968327 |
| 18 | 3610722528440693 |
| 19 | 26418301962683911 |
| 20 | 193292803059267825 |
| 21 | 1414250914660723047 |
[1,7,53,391,2865,20967,153413,1122471,8212705, 60089287,439650773,3216759751,23535824145, 172202794407,1259943234533,9218531904231, 67448539061185,493495652968327,3610722528440693, 26418301962683911,193292803059267825, 1414250914660723047] |