The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 20 |
| 3 | 266 |
| 4 | 1972 |
| 5 | 10784 |
| 6 | 48501 |
| 7 | 189595 |
| 8 | 665212 |
| 9 | 2138149 |
| 10 | 6384894 |
| 11 | 17895624 |
| 12 | 47447755 |
| 13 | 119746565 |
| 14 | 289136007 |
| 15 | 670787381 |
| 16 | 1500673676 |
| 17 | 3247602855 |
| 18 | 6817025467 |
| 19 | 13912884597 |
| 20 | 27665820296 |
| 21 | 53701416899 |
| 22 | 101922145950 |
| 23 | 189427147850 |
[0,20,266,1972,10784,48501,189595,665212,2138149, 6384894,17895624,47447755,119746565,289136007, 670787381,1500673676,3247602855,6817025467, 13912884597,27665820296,53701416899,101922145950, 189427147850] |