The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 2 |
| 3 | 8 |
| 4 | 34 |
| 5 | 120 |
| 6 | 468 |
| 7 | 1680 |
| 8 | 6530 |
| 9 | 23960 |
| 10 | 93532 |
| 11 | 348656 |
| 12 | 1366260 |
| 13 | 5149872 |
| 14 | 20238696 |
| 15 | 76907808 |
| 16 | 302903874 |
| 17 | 1158168792 |
| 18 | 4569270156 |
| 19 | 17555689008 |
| 20 | 69356428284 |
| 21 | 267518448912 |
| 22 | 1058057586456 |
| 23 | 4094231982048 |
| 24 | 16208177203764 |
| 25 | 62887835652720 |
| 26 | 249156625186328 |
| 27 | 968943740083040 |
| 28 | 3841488520364200 |
| 29 | 14968574892499040 |
| 30 | 59379627044952528 |
[0,0,2,8,34,120,468,1680,6530,23960,93532,348656, 1366260,5149872,20238696,76907808,302903874, 1158168792,4569270156,17555689008,69356428284, 267518448912,1058057586456,4094231982048, 16208177203764,62887835652720,249156625186328, 968943740083040,3841488520364200, 14968574892499040,59379627044952528] |