The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 21 |
| 3 | 77 |
| 4 | 1155 |
| 5 | 4389 |
| 6 | 33649 |
| 7 | 129789 |
| 8 | 4023459 |
| 9 | 15646785 |
| 10 | 122044923 |
| 11 | 477084699 |
| 12 | 7474326951 |
| 13 | 29322359577 |
| 14 | 230389968105 |
| 15 | 906200541213 |
| 16 | 57090634096419 |
| 17 | 225004263791769 |
| 18 | 1775033636579511 |
| 19 | 7006711723340175 |
| 20 | 110706045228774765 |
[1,3,21,77,1155,4389,33649,129789,4023459, 15646785,122044923,477084699,7474326951, 29322359577,230389968105,906200541213, 57090634096419,225004263791769,1775033636579511, 7006711723340175,110706045228774765] |