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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 31 |
| 3 | 283 |
| 4 | 2770 |
| 5 | 28204 |
| 6 | 294568 |
| 7 | 3131650 |
| 8 | 33732883 |
| 9 | 367035814 |
| 10 | 4025600941 |
| 11 | 44439461275 |
| 12 | 493218155119 |
| 13 | 5498860571026 |
| 14 | 61543476786067 |
| 15 | 691095770653867 |
| 16 | 7783168304357434 |
| 17 | 87878978740300960 |
| 18 | 994484816394177214 |
| 19 | 11276915136560900662 |
| 20 | 128106749179069022344 |
[1,4,31,283,2770,28204,294568,3131650,33732883, 367035814,4025600941,44439461275,493218155119, 5498860571026,61543476786067,691095770653867, 7783168304357434,87878978740300960, 994484816394177214,11276915136560900662, 128106749179069022344] |