The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 42 |
| 4 | 368 |
| 5 | 3920 |
| 6 | 49072 |
| 7 | 705040 |
| 8 | 11428608 |
| 9 | 206264064 |
| 10 | 4101145088 |
| 11 | 89058303488 |
| 12 | 2096974839808 |
| 13 | 53211247218688 |
| 14 | 1447517715093504 |
| 15 | 42021824434292736 |
| 16 | 1296647478998663168 |
| 17 | 42377209626843348992 |
| 18 | 1462318969075732971520 |
| 19 | 53128690694693099536384 |
| 20 | 2027179147327494593445888 |
[1,1,6,42,368,3920,49072,705040,11428608, 206264064,4101145088,89058303488,2096974839808, 53211247218688,1447517715093504,42021824434292736, 1296647478998663168,42377209626843348992, 1462318969075732971520,53128690694693099536384, 2027179147327494593445888] |