The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 4 |
| 5 | 16 |
| 6 | 53 |
| 7 | 160 |
| 8 | 512 |
| 9 | 1706 |
| 10 | 6144 |
| 11 | 23133 |
| 12 | 87380 |
| 13 | 327680 |
| 14 | 1217097 |
| 15 | 4508328 |
| 16 | 16777216 |
| 17 | 62914560 |
| 18 | 237677216 |
| 19 | 902444517 |
| 20 | 3435973836 |
| 21 | 13102206738 |
| 22 | 50026607709 |
| 23 | 191312691200 |
| 24 | 733007751680 |
| 25 | 2814062572336 |
| 26 | 10823317585920 |
| 27 | 41694907460224 |
| 28 | 160842843834660 |
[0,0,1,4,16,53,160,512,1706,6144,23133,87380, 327680,1217097,4508328,16777216,62914560, 237677216,902444517,3435973836,13102206738, 50026607709,191312691200,733007751680, 2814062572336,10823317585920,41694907460224, 160842843834660] |