The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 21 |
| 2 | 441 |
| 3 | 5246 |
| 4 | 41012 |
| 5 | 238366 |
| 6 | 1122522 |
| 7 | 4542734 |
| 8 | 16423026 |
| 9 | 54399996 |
| 10 | 167906334 |
| 11 | 488545330 |
| 12 | 1351296894 |
| 13 | 3575548984 |
| 14 | 9095336020 |
| 15 | 22330458551 |
| 16 | 53087335395 |
| 17 | 122539314344 |
| 18 | 275260139864 |
| 19 | 602890604743 |
| 20 | 1289688693983 |
| 21 | 2698414556120 |
[21,441,5246,41012,238366,1122522,4542734, 16423026,54399996,167906334,488545330,1351296894, 3575548984,9095336020,22330458551,53087335395, 122539314344,275260139864,602890604743, 1289688693983,2698414556120] |