The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 9 |
| 3 | 24 |
| 4 | 71 |
| 5 | 224 |
| 6 | 740 |
| 7 | 2496 |
| 8 | 8565 |
| 9 | 29792 |
| 10 | 104701 |
| 11 | 371304 |
| 12 | 1326702 |
| 13 | 4771380 |
| 14 | 17256161 |
| 15 | 62712800 |
| 16 | 228883359 |
| 17 | 838492436 |
| 18 | 3081972336 |
| 19 | 11361867384 |
| 20 | 41998361480 |
| 21 | 155620033360 |
| 22 | 577900838281 |
[4,9,24,71,224,740,2496,8565,29792,104701,371304, 1326702,4771380,17256161,62712800,228883359, 838492436,3081972336,11361867384,41998361480, 155620033360,577900838281] |