The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 12 |
| 3 | 66 |
| 4 | 484 |
| 5 | 4536 |
| 6 | 52128 |
| 7 | 709776 |
| 8 | 11153376 |
| 9 | 198339840 |
| 10 | 3932962560 |
| 11 | 85976743680 |
| 12 | 2053285148160 |
| 13 | 53173906652160 |
| 14 | 1483987541299200 |
| 15 | 44396218792396800 |
| 16 | 1417294759310438400 |
| 17 | 48088097391133900800 |
| 18 | 1728013936221838540800 |
| 19 | 65558270633421791232000 |
[1,3,12,66,484,4536,52128,709776,11153376, 198339840,3932962560,85976743680,2053285148160, 53173906652160,1483987541299200,44396218792396800, 1417294759310438400,48088097391133900800, 1728013936221838540800,65558270633421791232000] |