The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 0 |
| 3 | 0 |
| 4 | 6 |
| 5 | 0 |
| 6 | 180 |
| 7 | 630 |
| 8 | 1120 |
| 9 | 36288 |
| 10 | 441000 |
| 11 | 6579870 |
| 12 | 59734620 |
| 13 | 1252872192 |
| 14 | 13668490836 |
| 15 | 162131872695 |
| 16 | 2971275208720 |
| 17 | 52783774330940 |
| 18 | 1334562954639156 |
| 19 | 16933262255752698 |
| 20 | 406499325562503480 |
| 21 | 8838644883526856832 |
| 22 | 190698441426122689290 |
[1,1,0,0,6,0,180,630,1120,36288,441000,6579870, 59734620,1252872192,13668490836,162131872695, 2971275208720,52783774330940,1334562954639156, 16933262255752698,406499325562503480, 8838644883526856832,190698441426122689290] |