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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 6 |
| 3 | 14 |
| 4 | 50 |
| 5 | 242 |
| 6 | 1682 |
| 7 | 13442 |
| 8 | 134402 |
| 9 | 1612802 |
| 10 | 22579202 |
| 11 | 361267202 |
| 12 | 6864076802 |
| 13 | 144145612802 |
| 14 | 3459494707202 |
| 15 | 93406357094402 |
| 16 | 2802190712832002 |
| 17 | 92472293523456002 |
| 18 | 3421474860367872002 |
| 19 | 136858994414714880002 |
[4,6,14,50,242,1682,13442,134402,1612802,22579202, 361267202,6864076802,144145612802,3459494707202, 93406357094402,2802190712832002,92472293523456002, 3421474860367872002,136858994414714880002] |