The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 28 |
| 5 | 84 |
| 6 | 384 |
| 7 | 1824 |
| 8 | 6080 |
| 9 | 30400 |
| 10 | 304000 |
| 11 | 1064000 |
| 12 | 12768000 |
| 13 | 67488000 |
| 14 | 359936000 |
| 15 | 1934656000 |
| 16 | 30954496000 |
| 17 | 526226432000 |
| 18 | 2880397312000 |
| 19 | 15842185216000 |
| 20 | 316843704320000 |
| 21 | 1757042360320000 |
| 22 | 38654931927040000 |
[1,1,2,7,28,84,384,1824,6080,30400,304000,1064000, 12768000,67488000,359936000,1934656000, 30954496000,526226432000,2880397312000, 15842185216000,316843704320000,1757042360320000, 38654931927040000] |