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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 22 |
| 3 | 163 |
| 4 | 1564 |
| 5 | 18679 |
| 6 | 268714 |
| 7 | 4538209 |
| 8 | 88188280 |
| 9 | 1940666635 |
| 10 | 47744244286 |
| 11 | 1299383450941 |
| 12 | 38777402351476 |
| 13 | 1259552677645903 |
| 14 | 44247546748659130 |
| 15 | 1671904534990870369 |
| 16 | 67624237153933934704 |
| 17 | 2915628368081840175379 |
| 18 | 133499617770334938670198 |
[1,4,22,163,1564,18679,268714,4538209,88188280, 1940666635,47744244286,1299383450941, 38777402351476,1259552677645903,44247546748659130, 1671904534990870369,67624237153933934704, 2915628368081840175379,133499617770334938670198] |