The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 18 |
| 3 | 141 |
| 4 | 1027 |
| 5 | 7664 |
| 6 | 57471 |
| 7 | 430401 |
| 8 | 3222716 |
| 9 | 24132103 |
| 10 | 180705499 |
| 11 | 1353151672 |
| 12 | 10132613337 |
| 13 | 75874616631 |
| 14 | 568161175962 |
| 15 | 4254481072055 |
| 16 | 31858229585461 |
| 17 | 238559480074272 |
| 18 | 1786371253979085 |
| 19 | 13376631505148125 |
| 20 | 100166340017987924 |
[1,18,141,1027,7664,57471,430401,3222716,24132103, 180705499,1353151672,10132613337,75874616631, 568161175962,4254481072055,31858229585461, 238559480074272,1786371253979085, 13376631505148125,100166340017987924] |