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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 15 |
| 4 | 111 |
| 5 | 1071 |
| 6 | 12663 |
| 7 | 177255 |
| 8 | 2866671 |
| 9 | 52587711 |
| 10 | 1078805223 |
| 11 | 24470577495 |
| 12 | 608113846431 |
| 13 | 16429992037551 |
| 14 | 479502707791383 |
| 15 | 15032820820737735 |
| 16 | 503852219871917391 |
| 17 | 17978716725920562591 |
| 18 | 680458944566818819143 |
| 19 | 27227452811905815729975 |
| 20 | 1148414905826479180087551 |
[1,3,15,111,1071,12663,177255,2866671,52587711, 1078805223,24470577495,608113846431, 16429992037551,479502707791383,15032820820737735, 503852219871917391,17978716725920562591, 680458944566818819143,27227452811905815729975, 1148414905826479180087551] |