The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 21 |
| 2 | 441 |
| 3 | 5548 |
| 4 | 48182 |
| 5 | 319156 |
| 6 | 1721356 |
| 7 | 7906972 |
| 8 | 31947798 |
| 9 | 116289938 |
| 10 | 388293504 |
| 11 | 1205901516 |
| 12 | 3520937666 |
| 13 | 9746278721 |
| 14 | 25746339006 |
| 15 | 65246565981 |
| 16 | 159287861727 |
| 17 | 375892787585 |
| 18 | 859832700375 |
| 19 | 1910938878762 |
| 20 | 4134527627922 |
| 21 | 8723666100444 |
[21,441,5548,48182,319156,1721356,7906972, 31947798,116289938,388293504,1205901516, 3520937666,9746278721,25746339006,65246565981, 159287861727,375892787585,859832700375, 1910938878762,4134527627922,8723666100444] |