The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 12 |
| 4 | 408 |
| 5 | 13860 |
| 6 | 470832 |
| 7 | 15994428 |
| 8 | 543339720 |
| 9 | 18457556052 |
| 10 | 627013566048 |
| 11 | 21300003689580 |
| 12 | 723573111879672 |
| 13 | 24580185800219268 |
| 14 | 835002744095575440 |
| 15 | 963592443113182178088 |
| 16 | 32733777552734744709300 |
| 17 | 1111984844349868137938112 |
| 18 | 1283229546787304717998403160 |
[1,2,12,408,13860,470832,15994428,543339720, 18457556052,627013566048,21300003689580, 723573111879672,24580185800219268, 835002744095575440,963592443113182178088, 32733777552734744709300,1111984844349868137938112, 1283229546787304717998403160] |