The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 27 |
| 3 | 210 |
| 4 | 1730 |
| 5 | 14704 |
| 6 | 127470 |
| 7 | 1120262 |
| 8 | 9944676 |
| 9 | 88961008 |
| 10 | 800658947 |
| 11 | 7241596046 |
| 12 | 65764261576 |
| 13 | 599284477328 |
| 14 | 5477020329872 |
| 15 | 50182223592510 |
| 16 | 460796527028636 |
| 17 | 4239427396585840 |
| 18 | 39070459427293260 |
| 19 | 360622779428966656 |
| 20 | 3333138696913131830 |
| 21 | 30845466968858253248 |
[1,4,27,210,1730,14704,127470,1120262,9944676, 88961008,800658947,7241596046,65764261576, 599284477328,5477020329872,50182223592510, 460796527028636,4239427396585840, 39070459427293260,360622779428966656, 3333138696913131830,30845466968858253248] |