The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 12 |
| 3 | 74 |
| 4 | 484 |
| 5 | 3252 |
| 6 | 22260 |
| 7 | 154352 |
| 8 | 1080612 |
| 9 | 7621526 |
| 10 | 54071512 |
| 11 | 385454940 |
| 12 | 2758690636 |
| 13 | 19810063392 |
| 14 | 142662737376 |
| 15 | 1029931873824 |
| 16 | 7451492628260 |
| 17 | 54013574117106 |
| 18 | 392188079586468 |
| 19 | 2851934621212598 |
| 20 | 20766924805302984 |
| 21 | 151403389181347160 |
| 22 | 1105047483656041080 |
[2,12,74,484,3252,22260,154352,1080612,7621526, 54071512,385454940,2758690636,19810063392, 142662737376,1029931873824,7451492628260, 54013574117106,392188079586468,2851934621212598, 20766924805302984,151403389181347160, 1105047483656041080] |