The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 12 |
| 4 | 72 |
| 5 | 534 |
| 6 | 4818 |
| 7 | 50532 |
| 8 | 606408 |
| 9 | 8182656 |
| 10 | 122712912 |
| 11 | 2024328096 |
| 12 | 36432644400 |
| 13 | 710346495312 |
| 14 | 14915647605168 |
| 15 | 335567743462944 |
| 16 | 8052843408926976 |
| 17 | 205328108580310656 |
| 18 | 5543345188496499840 |
| 19 | 157970863597032124416 |
| 20 | 4738694884696030305024 |
[1,1,3,12,72,534,4818,50532,606408,8182656, 122712912,2024328096,36432644400,710346495312, 14915647605168,335567743462944,8052843408926976, 205328108580310656,5543345188496499840, 157970863597032124416,4738694884696030305024] |