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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 39 |
| 4 | 296 |
| 5 | 2435 |
| 6 | 21138 |
| 7 | 190603 |
| 8 | 1767968 |
| 9 | 16761424 |
| 10 | 161697576 |
| 11 | 1582171216 |
| 12 | 15664531716 |
| 13 | 156637712953 |
| 14 | 1579664567130 |
| 15 | 16048129755157 |
| 16 | 164085811289360 |
| 17 | 1687224436103842 |
| 18 | 17436287104620980 |
| 19 | 181001686332329224 |
| 20 | 1886522317836670988 |
| 21 | 19734386503541838083 |
[1,1,6,39,296,2435,21138,190603,1767968,16761424, 161697576,1582171216,15664531716,156637712953, 1579664567130,16048129755157,164085811289360, 1687224436103842,17436287104620980, 181001686332329224,1886522317836670988, 19734386503541838083] |