The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 12 |
| 6 | 40 |
| 7 | 74 |
| 8 | 300 |
| 9 | 538 |
| 10 | 2598 |
| 11 | 4682 |
| 12 | 25938 |
| 13 | 47292 |
| 14 | 296488 |
| 15 | 545820 |
| 16 | 3816240 |
| 17 | 7087260 |
| 18 | 54666830 |
| 19 | 102247562 |
| 20 | 862437450 |
| 21 | 1622632496 |
| 22 | 14857095400 |
| 23 | 28091567594 |
| 24 | 277474931700 |
| 25 | 526858348368 |
| 26 | 5584100612118 |
| 27 | 10641342969902 |
| 28 | 120462266677578 |
[1,1,1,2,6,12,40,74,300,538,2598,4682,25938,47292, 296488,545820,3816240,7087260,54666830,102247562, 862437450,1622632496,14857095400,28091567594, 277474931700,526858348368,5584100612118, 10641342969902,120462266677578] |