The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 720 |
| 7 | 4941 |
| 8 | 38736 |
| 9 | 341496 |
| 10 | 3354939 |
| 11 | 36244098 |
| 12 | 427006404 |
| 13 | 5448087216 |
| 14 | 74864913552 |
| 15 | 1102353646680 |
| 16 | 17314190063037 |
| 17 | 288936154260522 |
| 18 | 5105249306345502 |
| 19 | 95216905474054011 |
| 20 | 1869347069817467076 |
| 21 | 38535066745735462848 |
| 22 | 832195054189721911392 |
[1,1,2,6,24,120,720,4941,38736,341496,3354939, 36244098,427006404,5448087216,74864913552, 1102353646680,17314190063037,288936154260522, 5105249306345502,95216905474054011, 1869347069817467076,38535066745735462848, 832195054189721911392] |