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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 40 |
| 3 | 487 |
| 4 | 6376 |
| 5 | 86629 |
| 6 | 1203823 |
| 7 | 16984678 |
| 8 | 242274280 |
| 9 | 3484593028 |
| 10 | 50444222665 |
| 11 | 734066291974 |
| 12 | 10728052396111 |
| 13 | 157349171819155 |
| 14 | 2314894133906086 |
| 15 | 34145661019248487 |
| 16 | 504810905195542504 |
| 17 | 7478066502444399439 |
| 18 | 110972913533524676080 |
| 19 | 1649407167353221551706 |
| 20 | 24549982881130265421001 |
[1,4,40,487,6376,86629,1203823,16984678,242274280, 3484593028,50444222665,734066291974, 10728052396111,157349171819155,2314894133906086, 34145661019248487,504810905195542504, 7478066502444399439,110972913533524676080, 1649407167353221551706,24549982881130265421001] |