The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 12 |
| 4 | 96 |
| 5 | 600 |
| 6 | 9360 |
| 7 | 146160 |
| 8 | 1935360 |
| 9 | 41368320 |
| 10 | 1092268800 |
| 11 | 23111827200 |
| 12 | 700300339200 |
| 13 | 26141033318400 |
| 14 | 810322216704000 |
| 15 | 31624796915712000 |
| 16 | 1537594906079232000 |
| 17 | 63980698878480384000 |
| 18 | 3128302230597992448000 |
| 19 | 187447679378885173248000 |
[1,1,2,12,96,600,9360,146160,1935360,41368320, 1092268800,23111827200,700300339200, 26141033318400,810322216704000,31624796915712000, 1537594906079232000,63980698878480384000, 3128302230597992448000,187447679378885173248000] |