The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 0 |
| 3 | 1 |
| 4 | 3 |
| 5 | 6 |
| 6 | 14 |
| 7 | 40 |
| 8 | 140 |
| 9 | 422 |
| 10 | 1346 |
| 11 | 4487 |
| 12 | 15234 |
| 13 | 52632 |
| 14 | 183913 |
| 15 | 651948 |
| 16 | 2336751 |
| 17 | 8438406 |
| 18 | 30712379 |
| 19 | 112603500 |
| 20 | 415459873 |
| 21 | 1541646225 |
| 22 | 5750112809 |
| 23 | 21548036621 |
| 24 | 81096740799 |
| 25 | 306404247854 |
| 26 | 1161863199131 |
| 27 | 4420429256826 |
| 28 | 16869986745367 |
| 29 | 64567073382731 |
[1,1,0,1,3,6,14,40,140,422,1346,4487,15234,52632, 183913,651948,2336751,8438406,30712379,112603500, 415459873,1541646225,5750112809,21548036621, 81096740799,306404247854,1161863199131, 4420429256826,16869986745367,64567073382731] |