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 | 26 |
| 5 | 164 |
| 6 | 1540 |
| 7 | 22068 |
| 8 | 492616 |
| 9 | 17378968 |
| 10 | 977896328 |
| 11 | 88256247312 |
| 12 | 12819022165520 |
| 13 | 3002745820555664 |
| 14 | 1135759674922075168 |
| 15 | 694219521332053782624 |
| 16 | 686053892556368634929824 |
| 17 | 1096476587053610841771551296 |
| 18 | 2834651494015025836540377942080 |
[1,1,2,6,26,164,1540,22068,492616,17378968, 977896328,88256247312,12819022165520, 3002745820555664,1135759674922075168, 694219521332053782624,686053892556368634929824, 1096476587053610841771551296, 2834651494015025836540377942080] |