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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 38 |
| 3 | 330 |
| 4 | 2066 |
| 5 | 16994 |
| 6 | 116030 |
| 7 | 884792 |
| 8 | 6273952 |
| 9 | 46648918 |
| 10 | 335571098 |
| 11 | 2468592214 |
| 12 | 17883911418 |
| 13 | 130889355348 |
| 14 | 951392168734 |
| 15 | 6947056359884 |
| 16 | 50571064277718 |
| 17 | 368890128041664 |
| 18 | 2687133002363550 |
| 19 | 19592211767424272 |
| 20 | 142760104420636614 |
[4,38,330,2066,16994,116030,884792,6273952, 46648918,335571098,2468592214,17883911418, 130889355348,951392168734,6947056359884, 50571064277718,368890128041664,2687133002363550, 19592211767424272,142760104420636614] |