The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 25 |
| 5 | 122 |
| 6 | 728 |
| 7 | 5066 |
| 8 | 40444 |
| 9 | 363618 |
| 10 | 3633894 |
| 11 | 39957372 |
| 12 | 479365980 |
| 13 | 6230659848 |
| 14 | 87218289408 |
| 15 | 1308154099944 |
| 16 | 20929024197336 |
| 17 | 355774686465840 |
| 18 | 6403682340295200 |
| 19 | 121666035674658960 |
| 20 | 2433257870201802720 |
| 21 | 51097347163646718480 |
| 22 | 1124122414761046131120 |
[1,1,2,7,25,122,728,5066,40444,363618,3633894, 39957372,479365980,6230659848,87218289408, 1308154099944,20929024197336,355774686465840, 6403682340295200,121666035674658960, 2433257870201802720,51097347163646718480, 1124122414761046131120] |