The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 28 |
| 5 | 136 |
| 6 | 544 |
| 7 | 2080 |
| 8 | 8128 |
| 9 | 32512 |
| 10 | 130816 |
| 11 | 524800 |
| 12 | 2099200 |
| 13 | 8390656 |
| 14 | 33550336 |
| 15 | 134201344 |
| 16 | 536854528 |
| 17 | 2147516416 |
| 18 | 8590065664 |
| 19 | 34359869440 |
| 20 | 137438691328 |
| 21 | 549754765312 |
| 22 | 2199022206976 |
| 23 | 8796095119360 |
| 24 | 35184380477440 |
| 25 | 140737496743936 |
| 26 | 562949936644096 |
[1,1,1,4,28,136,544,2080,8128,32512,130816,524800, 2099200,8390656,33550336,134201344,536854528, 2147516416,8590065664,34359869440,137438691328, 549754765312,2199022206976,8796095119360, 35184380477440,140737496743936,562949936644096] |