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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 20 |
| 4 | 299 |
| 5 | 3970 |
| 6 | 49401 |
| 7 | 590040 |
| 8 | 6850999 |
| 9 | 77919950 |
| 10 | 872348501 |
| 11 | 9645565060 |
| 12 | 105583302099 |
| 13 | 1146187455930 |
| 14 | 12356291257201 |
| 15 | 132416725116080 |
| 16 | 1411810959903599 |
| 17 | 14985692873919910 |
| 18 | 158445117779295501 |
| 19 | 1669465484919035100 |
| 20 | 17536209731411055499 |
| 21 | 183692631829191519890 |
| 22 | 1919390108560504143401 |
[0,1,20,299,3970,49401,590040,6850999,77919950, 872348501,9645565060,105583302099,1146187455930, 12356291257201,132416725116080,1411810959903599, 14985692873919910,158445117779295501, 1669465484919035100,17536209731411055499, 183692631829191519890,1919390108560504143401] |