The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 2 |
| 1 | 6 |
| 2 | 24 |
| 3 | 100 |
| 4 | 422 |
| 5 | 1786 |
| 6 | 7564 |
| 7 | 32040 |
| 8 | 135722 |
| 9 | 574926 |
| 10 | 2435424 |
| 11 | 10316620 |
| 12 | 43701902 |
| 13 | 185124226 |
| 14 | 784198804 |
| 15 | 3321919440 |
| 16 | 14071876562 |
| 17 | 59609425686 |
| 18 | 252509579304 |
| 19 | 1069647742900 |
| 20 | 4531100550902 |
| 21 | 19194049946506 |
| 22 | 81307300336924 |
| 23 | 344423251294200 |
| 24 | 1459000305513722 |
| 25 | 6180424473349086 |
[2,6,24,100,422,1786,7564,32040,135722,574926, 2435424,10316620,43701902,185124226,784198804, 3321919440,14071876562,59609425686,252509579304, 1069647742900,4531100550902,19194049946506, 81307300336924,344423251294200,1459000305513722, 6180424473349086] |