The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 4 |
| 2 | 8 |
| 3 | 16 |
| 4 | 48 |
| 5 | 124 |
| 6 | 320 |
| 7 | 844 |
| 8 | 2208 |
| 9 | 5776 |
| 10 | 15128 |
| 11 | 39604 |
| 12 | 103680 |
| 13 | 271444 |
| 14 | 710648 |
| 15 | 1860496 |
| 16 | 4870848 |
| 17 | 12752044 |
| 18 | 33385280 |
| 19 | 87403804 |
| 20 | 228826128 |
| 21 | 599074576 |
| 22 | 1568397608 |
| 23 | 4106118244 |
| 24 | 10749957120 |
| 25 | 28143753124 |
| 26 | 73681302248 |
| 27 | 192900153616 |
| 28 | 505019158608 |
| 29 | 1322157322204 |
[0,4,8,16,48,124,320,844,2208,5776,15128,39604, 103680,271444,710648,1860496,4870848,12752044, 33385280,87403804,228826128,599074576,1568397608, 4106118244,10749957120,28143753124,73681302248, 192900153616,505019158608,1322157322204] |