The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 17 |
| 5 | 81 |
| 6 | 441 |
| 7 | 3641 |
| 8 | 33825 |
| 9 | 318753 |
| 10 | 3505521 |
| 11 | 45095601 |
| 12 | 616484001 |
| 13 | 9013086369 |
| 14 | 145909533225 |
| 15 | 2556431401161 |
| 16 | 47388760825281 |
| 17 | 937507626246081 |
| 18 | 19840711661183457 |
| 19 | 443937299529447009 |
| 20 | 10456231167451597761 |
| 21 | 259738234024404363201 |
[1,1,1,3,17,81,441,3641,33825,318753,3505521, 45095601,616484001,9013086369,145909533225, 2556431401161,47388760825281,937507626246081, 19840711661183457,443937299529447009, 10456231167451597761,259738234024404363201] |